| 1. |
- Abdullah, Muhammad Imran, et al.
(författare)
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Quantum Chemical Designing of Efficient Sensitizers for Dye Sensitized Solar Cells
- 2013
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Ingår i: Bulletin of the Korean Chemical Society (Print). - : Korean Chemical Society. - 0253-2964 .- 1229-5949. ; 34:7, s. 2093-2098
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Tidskriftsartikel (refereegranskat)abstract
- Density functional theory (DFT) was used to determine the ground state geometries of indigo and new design dyes (IM-Dye-1 IM-Dye-2 and IM-Dye-3). The time dependant density functional theory (TDDFT) was used to calculate the excitation energies. All the calculations were performed in both gas and solvent phase. The LUMO energies of all the dyes were above the conduction band of TiO2, while the HOMOs were below the redox couple (except IM-Dye-3). The HOMO-LUMO energy gaps of new design dyes were smaller as compared to indigo. All new design dyes were strongly red shifted as compared to indigo. The improved light harvesting efficiency (LHE) and free energy change of electron injection Delta G(inject) of new designed sensitizers revealed that these materials would be excellent sensitizers. The broken coplanarity between the benzene near anchoring group having LUMO and the last benzene attached to TPA unit in all new design dyes consequently would hamper the recombination reaction. This theoretical designing will the pave way for experimentalists to synthesize the efficient sensitizers for solar cells.
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| 2. |
- Azeem, Muhammad, et al.
(författare)
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Design, synthesis, spectroscopic characterization, in-vitro antibacterial evaluation and in-silico analysis of polycaprolactone containing chitosan-quercetin microspheres
- 2023
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Ingår i: Journal of Biomolecular Structure and Dynamics. - : TAYLOR & FRANCIS INC. - 0739-1102 .- 1538-0254. ; 41:15, s. 7084-7103
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Tidskriftsartikel (refereegranskat)abstract
- Aim of present study was to synthesize a novel chitosan-quercetin (CTS-QT) complex by making a carbodiimide linkage using maleic anhydride as cross-linker and to investigate its enhanced antibacterial and antioxidant activities as compare to pure CTS and QT. Equimolar concentration of QT and maleic anhydride were used to react with 100 mg CTS to form CTS-QT complex. For this purpose, three bacterial strains namely E. Coli, S. Aureus and P. Aeruginosa were used for in-vitro antibacterial analysis (ZOI, MIC, MBC, checker board and time kill assay). Later molecular docking studies were performed on protein structure of E. Coli to assess binding affinity of pure QT and CTS-QT complex. MD simulations with accelerated settings were used to explore the protein-ligand complexs binding interactions and stability. Antioxidant profile was determined by performing DPPH center dot radical scavenging assay, total antioxidant capacity (TAC) and total reducing power (TRP) assays. Delivery mechanism to CTS-QT complex was improved by synthesizing polycaprolactone containing microspheres (CTS-QT-PCL-Levo-Ms) using Levofloxacin as model drug to enhance their antibacterial profile. Resulted microspheres were evaluated by particle size, charge, surface morphology, in-vitro drug release and hemolytic profile and are all were found within limits. Antibacterial assay revealed that CTS-QT-PCL-Levo-Ms showed more than two folds increased bactericidal activity against E. Coli and P. Aeruginosa, while 1.5 folds against S. Aureus. Green colored formation of phosphate molybdate complexes with highest 85 +/- 1.32% TAC confirmed its antioxidant properties. Furthermore, molecular docking and dynamics studies revealed that CTS-QT was embedded nicely within the active pocket of UPPS with binding energy greater than QT with RSMD value of below 1.5. Conclusively, use of maleic acid, in-vitro and in-silico antimicrobial studies confirm the emergence of CTS-QT complex containing microspheres as novel treatment strategy for all types of bacterial infections. Communicated by Ramaswamy H. Sarma
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| 3. |
- Zulfiqar, Shumaila, et al.
(författare)
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Identification of a novel variant in GPR56/ADGRG1 gene through whole exome sequencing in a consanguineous Pakistani family
- 2021
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Ingår i: Journal of clinical neuroscience. - : Elsevier. - 0967-5868 .- 1532-2653. ; 94, s. 8-12
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Tidskriftsartikel (refereegranskat)abstract
- GPR56 gene is best known for its pivotal role in cerebral cortical development. Mutations in GPR56 give rise to cobblestone-like brain malformation, white matter changes and cerebellar dysplasia. This study aimed to identify causative variant in a consanguineous family having five individuals affected with developmental delay, mild to severe intellectual disability, speech impairment, strabismus and seizures. Whole exome sequencing was performed to identify mutation in affected individuals. Variants were filtered and further validated by Sanger sequencing and segregation analysis. A novel frameshift variant c.1601dupT leading to p.Ala535GlyfsTer17) was identified in GPR56 gene by whole exome sequencing and subsequent filtering. All five affected individuals were homozygous for the mutant allele while four asymptomatic individuals carried the variant in heterozygous state. Radiological findings of a representative patient presented features of GPR56-associated cobblestone like brain malformation. MRI findings suggested paucity of sulci, dilated ventricular system and brainstem atrophy. The microgyria were observed in a simplified gyral pattern (cobblestone). This single bp insertion, and the consequent frame-shift, results in the truncation of GPR56 protein. This could result in a malformed cortex giving the brain a cobblestone like shape. Our study identified a 7th novel frameshift variant from Pakistani population in GPR56 gene, thus broadening mutation spectrum.
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| 4. |
- Araujo, Carlos Moyses, et al.
(författare)
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Disorder-induced Room Temperature Ferromagnetism in Glassy Chromites
- 2014
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4, s. 4686-
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Tidskriftsartikel (refereegranskat)abstract
- We report an unusual robust ferromagnetic order above room temperature upon amorphization of perovskite [YCrO3] in pulsed laser deposited thin films. This is contrary to the usual expected formation of a spin glass magnetic state in the resulting disordered structure. To understand the underlying physics of this phenomenon, we combine advanced spectroscopic techniques and first-principles calculations. We find that the observed order-disorder transformation is accompanied by an insulator-metal transition arising from a wide distribution of Cr-O-Cr bond angles and the consequent metallization through free carriers. Similar results also found in YbCrO3-films suggest that the observed phenomenon is more general and should, in principle, apply to a wider range of oxide systems. The ability to tailor ferromagnetic order above room temperature in oxide materials opens up many possibilities for novel technological applications of this counter intuitive effect.
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| 5. |
- Arslanov, Temirlan R., et al.
(författare)
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Pressure control of magnetic clusters in strongly inhomogeneous ferromagnetic chalcopyrites
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5, s. 7720-
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Tidskriftsartikel (refereegranskat)abstract
- Room-temperature ferromagnetism in Mn-doped chalcopyrites is a desire aspect when applying those materials to spin electronics. However, dominance of high Curie-temperatures due to cluster formation or inhomogeneities limited their consideration. Here we report how an external perturbation such as applied hydrostatic pressure in CdGeP2:Mn induces a two serial magnetic transitions from ferromagnet to non-magnet state at room temperature. This effect is related to the unconventional properties of created MnP magnetic clusters within the host material. Such behavior is also discussed in connection with ab initio density functional calculations, where the structural properties of MnP indicate magnetic transitions as function of pressure as observed experimentally. Our results point out new ways to obtain controlled response of embedded magnetic clusters.
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| 6. |
- Belonoshko, Anatoly B., et al.
(författare)
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Atomic Diffusion in Solid Molecular Hydrogen
- 2013
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3, s. 2340-
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Tidskriftsartikel (refereegranskat)abstract
- We performed ab initio molecular dynamics simulations of the C2c and Cmca-12 phases of hydrogen at pressures from 210 to 350 GPa. These phases were predicted to be stable at 0 K and pressures above 200 GPa. However, systematic studies of temperature impact on properties of these phases have not been performed so far. Filling this gap, we observed that on temperature increase diffusion sets in the Cmca-12 phase, being absent in C2c. We explored the mechanism of diffusion and computed melting curve of hydrogen at extreme pressures. The results suggest that the recent experiments claiming conductive hydrogen at the pressure around 260 GPa and ambient temperature might be explained by the diffusion. The diffusion might also be the reason for the difference in Raman spectra obtained in recent experiments.
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| 7. |
- Huang, L., et al.
(författare)
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Anomalous temperature dependence of elastic constant c(44) in V, Nb, Ta, Pd, and Pt
- 2010
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Ingår i: Journal of Physics and Chemistry of Solids. - : Elsevier BV. - 0022-3697 .- 1879-2553. ; 71:8, s. 1065-1068
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Tidskriftsartikel (refereegranskat)abstract
- The anomalous temperature dependence of elastic constant c(44) for elements V. Nb, Ta, Pd, and Pt, has been calculated using first-principles theory. It is shown that the variation of elastic constant for simple elements can be approximated as the sum of thermal expansion and electronic components. The thermal expansion contributes the normal linearly decreasing effect to the elastic constant with temperature, while electronic contribution is determined by the unique character of electronic structure of elements and leads to the anomalous effect to the elastic constant with temperature.
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| 8. |
- Hussain, Tanveer, et al.
(författare)
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Calcium doped graphane as a hydrogen storage material
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:18, s. 183902-
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Tidskriftsartikel (refereegranskat)abstract
- On the basis of first principle density functional theory, we have studied the stability, electronic structure, and hydrogen storage capacity of a monolayer calcium doped graphane (CHCa). The stability of CHCa was further investigated using the ab initio molecular dynamics study. The binding energy of Ca on graphane sheet was found to be higher than its bulk cohesive energy, which indicates the stability of CHCa. It was observed that with a doping concentration of 11.11% of Ca on graphane sheet, a reasonably good H-2 storage capacity of 6 wt. % could be attained. The adsorption energies of H-2 were found to be 0.1 eV, within the range of practical H-2 storage applications.
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| 9. |
- Hussain, Tanveer, et al.
(författare)
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Functionalization of graphane with alkali and alkaline-earth metals : An insulator-to-metallic transition
- 2012
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 99:4, s. 47004-
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Tidskriftsartikel (refereegranskat)abstract
- In view of interest in functionalized carbon nanostructures due to their potential applications in nanotechnology and nanoelectronics, we have performed a systematic and thorough density functional theory (DFT) study on the interaction of the elements in the first two groups of the periodic table with graphane (hydrogenated graphene) sheet. GGA approximation as employed in DFT has been used to study in detail the binding configuration, bond length, charge transfer and band gap of each of these adatoms doped graphane (CH) systems. To have a better understanding of the adatoms-CH interaction, different doping concentrations varying from 3.125% to 50% have been considered. A certain trend in binding strength, bond length and charge transfer has been found in the case of both alkali metal and alkaline-earth metal adatoms. In the case of alkali-metal adatoms at the low doping concentration of 3.125%, semiconductor behavior was found, whereas at doping higher than this the compound showed metallic behavior. In contrast, alkaline-earth metal-doped CH exhibited metallic behavior at all the doping concentrations.
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| 10. |
- Kaewmaraya, Thanayut, et al.
(författare)
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Atomistic study of promising catalyst and electrode material for memory capacitors : Platinum oxides
- 2013
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Ingår i: Computational materials science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 79, s. 804-810
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Tidskriftsartikel (refereegranskat)abstract
- Platinum oxides have the technological importance as evidenced by numerous studies concentrating on their crystal structures to attain the clear atomistic understanding but the controversy exists between the experimental and theoretical studies. In our present study, we report the electronic and optical properties of crystalline PtO and PtO2 on the basis of Heyd-Scuseria-Ernzerhof (HSE06) functional within the framework of the density functional theory (DFT). We present the structural parameters, electronic and optical properties of several proposed structures of PtO and PtO2. We find that PtS-type structure of PtO and CaCl2-type structure of PtO2 are the most stable structures of these materials on the basis of hybrid functional and they appear to be semiconductors with band gap values of 0.87 eV and 1.85 eV, respectively. The mechanical stability of these structures is also confirmed by calculating the phonon band structures. The corresponding structural parameters are found in good agreement with experimental values. Furthermore, we present the bader charge analysis and optical properties of these phases.
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| 11. |
- Kaewmaraya, Thanayut, et al.
(författare)
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Electronic structure and ionic diffusion of green battery cathode material : Mg2Mo6S8
- 2014
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738 .- 1872-7689. ; 261, s. 17-20
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Tidskriftsartikel (refereegranskat)abstract
- We report ab-initio density functional theory calculations of crystal and electronic structure of Mg2Mo6S8, a candidate material to be used in rechargeable magnesium batteries, by employing hybrid exchange-correlation functionals. We find that Mg2Mo6S8 crystalizes in a triclinic geometry and it is a semiconductor with an indirect band gap. Ab-initio molecular dynamics shows that Mg ions present progressive diffusion starting at 200 K with a preferable path through the channel between Mo6S8 blocks along the [010] direction. The intercalation voltage of the system is also determined and the results show that the voltage evaluated by PBE and hybrid functionals likely implies the lower and the upper limit of the experimental value. Lastly, we confirm the dynamical stability of the crystal structure by the calculated phonon dispersion relation.
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| 12. |
- Kaewmaraya, Thanayut, et al.
(författare)
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Hybrid density functional study of electronic and optical properties of phase change memory material : Ge2Sb2Te5
- 2013
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 113:3, s. 033510-
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we use hybrid density functional (HSE06) to study the crystal and electronic structures and optical properties of well known phase change memory material Ge2Sb2Te5. We calculate the structural parameters, band gaps, and dielectric functions of three stable structures of this material. We also analyze the electron charge distribution using the Bader's theory of charge analysis. We find that hybrid density functional slightly overestimates the value of "c" parameter. However, overall, our results calculated with the use of hybrid density functional (HSE06) are very close to available experimental values than calculated with the use of Perdew Burke-Ernzerhof functional. Specifically, the electronic band gap values of this material calculated with HSE06 are in good agreement with the available experimental data in the literature. Furthermore, we perform the charge analysis and find that naive ionic model fails to explain the charge distribution between the constituent atoms, showing the complex nature of this compound.
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| 13. |
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| 14. |
- Lebegue, Sebastien, et al.
(författare)
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Semimetallic dense hydrogen above 260 GPa
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:25, s. 9766-9769
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Tidskriftsartikel (refereegranskat)abstract
- Being the lightest and the most abundant element in the universe, hydrogen is fascinating to physicists. In particular, the conditions of its metallization associated with a possible superconducting state at high temperature have been a matter of much debate in the scientific community, and progress in this field is strongly correlated with the advancements in theoretical methods and experimental techniques. Recently, the existence of hydrogen in a metallic state was reported experimentally at room temperature under a pressure of 260-270 GPa, but was shortly after that disputed in the light of more experiments, finding either a semimetal or a transition to an other phase. With the aim to reconcile the different interpretations proposed, we propose by combining several computational techniques, such as density functional theory and the GW approximation, that phase III at ambient temperature of hydrogen is the Cmca-12 phase, which becomes a semimetal at 260 GPa. From phonon calculations, we demonstrate it to be dynamically stable; calculated electron-phonon coupling is rather weak and therefore this phase is not expected to be a high-temperature superconductor.
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| 15. |
- Lizarraga, Raquel, et al.
(författare)
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Structural characterization of amorphous YCrO3 from first principles
- 2012
-
Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 99:5, s. 57010-
-
Tidskriftsartikel (refereegranskat)abstract
- We perform a theoretical prediction of the structure of amorphous YCrO3. We obtained equivalent amorphous structures by means of two independent first principles density functional theory based methods: molecular dynamics and stochastic quenching. In our structural analysis we include radial and angle distribution functions as well as calculations of bond lengths and average coordination numbers. We find Cr+3 atoms situated in slightly distorted oxygen octahedra throughout the amorphous structures and that the distribution of these octahedra is disordered. The presence of the same Cr+3 local environments that give rise to ferroelectricity in the orthorhombic perovskite structure suggests that the amorphous phase of YCrO3 may also exhibit ferroelectric properties. Copyright (c) EPLA, 2012
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| 16. |
- Lykissa, Iliana, et al.
(författare)
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Electronic density-of-states of amorphous vanadium pentoxide films : Electrochemical data and density functional theory calculations
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:18, s. 183701/1-/5
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of V2O5 were prepared by sputter deposition onto transparent and electrically conducting substrates and were found to be X-ray amorphous. Their electrochemical density of states was determined by chronopotentiometry and displayed a pronounced low-energy peak followed by an almost featureless contribution at higher energies. These results were compared with density functional theory calculations for amorphous V2O5. Significant similarities were found between measured data and computations; specifically, the experimental low-energy peak corresponds to a split-off part of the conduction band apparent in the computations. Furthermore, the calculations approximately reproduce the experimental band gap observed in optical measurements.
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| 17. |
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| 18. |
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| 19. |
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| 20. |
- Ozaki, N., et al.
(författare)
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Dynamic compression of dense oxide (Gd3Ga5O12) from 0.4 to 2.6 TPa : Universal Hugoniot of fluid metals
- 2016
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Materials at high pressures and temperatures are of great current interest for warm dense matter physics, planetary sciences, and inertial fusion energy research. Shock-compression equation-of-state data and optical reflectivities of the fluid dense oxide, Gcl(3)Ga(5)O(12) (GGG), were measured at extremely high pressures up to 2.6TPa (26 Mbar) generated by high-power laser irradiation and magnetically driven hypervelocity impacts. Above 0.75TPa, the GGG Hugoniot data approach/reach a universal linear line of fluid metals, and the optical reflectivity most likely reaches a constant value indicating that GGG undergoes a crossover from fluid semiconductor to poor metal with minimum metallic conductivity (MMC). These results suggest that most fluid compounds, e.g., strong planetary oxides, reach a common state on the universal Hugoniot of fluid metals (UHFM) with MMC at sufficiently extreme pressures and temperatures. The systematic behaviors of warm dense fluid would be useful benchmarks for developing theoretical equation-of-state and transport models in the warm dense matter regime in determining computational predictions.
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| 21. |
- Ramzan, Muhammad, et al.
(författare)
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Ab initio molecular dynamics study of the hydrogen-deuterium exchange in bulk lithiumborohydride (LiBH4)
- 2009
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:14, s. 141903-
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Tidskriftsartikel (refereegranskat)abstract
- The hydrogen storage is still a challenge for mobile applications. The diffusion of hydrogen in solids is considered as a general model system but there is limited knowledge available for the dynamics of hydrogen in complex hydrides. In this letter, we present a systematic approach to study the hydrogen-deuterium exchange in bulk LiBH4 based on ab initio molecular dynamics. Our results predict the single hydrogen (deuterium) exchange in LiBH4, which supports the experimental results. The self-diffusion constant < D > of deuterium in LiBH4 is around 1.42x10(-8) m(2) s(-1).
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| 22. |
- Ramzan, Muhammad, et al.
(författare)
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Ab initio molecular dynamics study of the hydrogen diffusion in sodium and lithium hydrides
- 2009
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 106:1
-
Tidskriftsartikel (refereegranskat)abstract
- Light weight complex metal hydrides, sodium hydride (NaH), and lithium hydride (LiH) are the last step materials during hydrogen release process of alanates and borates, which are promising candidates for hydrogen storage. We report ab initio molecular dynamics (MD) calculations based on density functional theory to study the hydrogen-deuterium exchange in NaH and LiH. We predict the single hydrogen-deuterium exchange in NaH and LiH and calculate the self-diffusion constants, << D >>(NaH)approximate to 1.46x10(-9) m(2) s(-1) of deuterium in NaH at 420 K and << D >>(LiH)approximate to 1.49x10(-9) m(2) s(-1) of deuterium in LiH at 550 K, which are in good agreement with the experimental values.
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| 23. |
- Ramzan, Muhammad, et al.
(författare)
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Correlation effects in the electronic and structural properties of Cr2AlC
- 2011
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Ingår i: PHYS STATUS SOLIDI-RAPID RE L. - : Wiley. - 1862-6254 .- 1862-6270. ; 5:3, s. 122-124
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Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we present the electronic and structural properties calculated by first principles GGA and GGA+U calculations of Cr2AlC, a member of the MAX phases family of compounds. While GGA fails to obtain a correct description, the GGA+U method successfully reproduces the experimental equilibrium volume and bulk modulus values of Cr2AlC, and predict it to be a ferromagnet. Therefore, correlation effects are crucial for the correct description of Cr2AlC, provided that a suitable value of U is chosen.
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| 24. |
- Ramzan, Muhammad, et al.
(författare)
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Crystal and electronic structures of lithium fluorosulphate based materials for lithium-ion batteries
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 82:12, s. 125101-
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Tidskriftsartikel (refereegranskat)abstract
- By means of ab initio calculations, we study the electronic structure of LiFeSO4F, which has been shown recently [N. Recham et al., Nature Mater. 9, 68 (2010)] to be an excellent material as a cathode for lithium-ion batteries. We have obtained the crystal structure of FeSO4F, which was not completely determined experimentally, and compare the one of LiFeSO4F to available experimental values, resolving the issue about the position of the Li ion. Our calculated intercalation voltage (3.69 V) is found to be in excellent agreement with experiments. Finally, we have studied LiCoSO4F and LiNiSO4F, which are found to share a similar crystal structure with LiFeSO4F.
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| 25. |
- Ramzan, Muhammad, et al.
(författare)
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Electronic and mechanical properties of Cr2GeC with hybrid functional and correlation effects
- 2012
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 152:13, s. 1147-1149
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Tidskriftsartikel (refereegranskat)abstract
- We present a computational study of the MAX phase material Cr2GeC to obtain its crystal and electronic structure using density functional theory with various exchange-correlation functionals. While the GGA and GGA+U methods are giving a reasonable description of the lattice parameters, the hybrid functional (HSE06) is found to give too large values. Then, on the basis of our GGA+U calculations, the antiferromagnetic ordering is found to be the ground state. Furthermore, we study the charge distribution between the constituent elements of this compound and find that the simple ionic model fails to describe it due to the complex nature of this material. Finally, we conclude that the treatment of the correlated electrons is important for the correct description of this material.
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| 26. |
- Ramzan, Muhammad, et al.
(författare)
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Electronic, mechanical and optical properties of Y2O3 with hybrid density functional (HSE06)
- 2013
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Ingår i: Computational materials science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 71, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we have investigated the electronic, optical and mechanical properties of the Y2O3 crystal by first-principle calculations based on the density-functional theory. The generalized gradient approximation (GGA-PBE) and hybrid exchange-correlation functional (HSE06) are both used for comparative study. It is found that, the band gap of Y2O3 calculated by HSE06 method (6.0 eV) is in good agreement with the experimental band gap data (5.5 eV), and HSE06 gives better electronic structure description close to experiments. Then we calculate the elastic constants, and derive the corresponding properties i.e.; bulk, shear and Young's moduli, and Poisson's ratio. Our calculated elastic and mechanical properties correspond well with experimental data. Besides, we also obtain the equilibrium lattice and bulk modulus of yttria by fitting the Birch-Murnaghan equation of state. It is found that, the HSE06 well reproduce the experimental lattice parameters, equilibrium volume and bulk modulus of Y2O3. Based on the accurate described crystal and electronic structure and mechanical properties by HSE06 method, the optical properties of this material are also analyzed.
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| 27. |
- Ramzan, Muhammad, et al.
(författare)
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Electronic structure and metalization of a silane-hydrogen system under high pressure investigated using density functional and GW calculations
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:23, s. 233103-
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Tidskriftsartikel (refereegranskat)abstract
- We have computed the electronic structure and the vibrational properties of the recently discovered hydrogen-rich compound silane-hydrogen [SiH4(H-2)(2)] from first principles, using density-functional theory. We have also studied the metallization under pressure of SiH4(H-2)(2) by the GW approximation, and obtained that the metallization occurs around 164 GPa, whereas the standard GGA calculations predict a metallization pressure around 145 GPa. Our results are compared with the recent experiment data of Strobel et al. [Phys. Rev. Lett. 103, 065701 (2009)] and Wang et al. [Proc. Natl. Acad. Sci. USA. 106, 14763 (2009)] and it is found that our calculated value of the metallization pressure is higher than the proposed experimental data. Some possible reasons for such a discrepancy are discussed in the text.
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| 28. |
- Ramzan, Muhammad, et al.
(författare)
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Electronic Structure from First-Principles of LiBH(4)center dot NH(3), Sr(NH(2)BH(3))(2), and Li(2)Al(BH(4))(5)center dot 6NH(3) for Hydrogen Storage Applications
- 2011
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:40, s. 20036-20042
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Tidskriftsartikel (refereegranskat)abstract
- A series of compounds containing boron, nitrogen, and hydrogen atoms, namely, LiBH(4)center dot NH(3), Sr(NH(2)BH(3))(2), and Li(2)Al(BH(4))(5)center dot 6NH(3), were synthesized recently, and found to be promising for hydrogen storage. We have conducted the corresponding ab initio calculations using density functional theory and analyzed the corresponding electron density as well as derived properties. Also, molecular dynamics simulations were performed to study the diffusion of hydrogen in this series of compounds. We found that despite having widely different crystal structures and difference in their chemical composition, these compounds share common features at the level of their electronic structure. Moreover, diffusion of hydrogen appears to be more favorable in LiBH(4)center dot NH(3) than in Sr(NH(2)BH(3))(2) and Li(2)Al(BH(4))(5)center dot 6NH(3).
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| 29. |
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| 30. |
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| 31. |
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| 32. |
- Ramzan, Muhammad, et al.
(författare)
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Ferromagnetism in the potential cathode material LiNaFePO4F
- 2009
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 87:1
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Tidskriftsartikel (refereegranskat)abstract
- We present the ab initio study of the cathode material LiNaFePO4F, which is suitable for rechargeable batteries. Our calculations reveal the ferromagnetic order to be the ground state of this material. We also predict more than 5.0V intercalation voltage of this material for sodium-ion batteries. The low cost of sodium iron. fluorophasphate batteries and more than 5.0V intercalation voltage makes it the more suitable candidate, commercially and scientifically, than any other cathode materials for rechargeable batteries.
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| 33. |
- Ramzan, Muhammad, et al.
(författare)
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High pressure and temperature study of hydrogen storage material BH3NH3 from ab initio calculations
- 2010
-
Ingår i: Journal of Physics and Chemistry of Solids. - : Elsevier BV. - 0022-3697 .- 1879-2553. ; 71:8, s. 1137-1139
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Tidskriftsartikel (refereegranskat)abstract
- We report on BH3NH3, which is material considered promising to use as hydrogen storage, using density functional theory with generalized gradient approximation (GGA). We study the phase transition of BH3NH3 at high pressure and temperature. Our observed phase transition of BH3NH3 from body-centered tetragonal to orthorhombic at 220 K supports the recent and earlier studies. We observe the phase transformation of BH3NH3 at approximate to 11.5 GPa, which is in good agreement with experimental value. Specifically, we predict the phase transition at 11.5 GPa to be orthorhombic to body-centered tetragonal on the basis of our first principles calculations.
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| 34. |
- Ramzan, Muhammad, et al.
(författare)
-
High pressure, mechanical, and optical properties of ZrW2O8
- 2011
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 109:3, s. 033510-
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present the high pressure studies of well known negative thermal expansion material ZrW2O8 on the basis of our density functional theory calculations. We reproduce the experimental alpha and gamma crystal structures of ZrW2O8. We calculate the transition pressure (from alpha to gamma) of this material to be approximate to 26 kbar. Our calculated positional and axial parameters are in an excellent agreement with the available experimental values for the both alpha and gamma phases of this material. Then we study the mechanical properties of this material. We calculate the elastic constants, bulk, shear and Young's moduli, Poisson's ratio, and Debye temperature of alpha-ZrW2O8. In our study, we find that the generalized gradient approximation method fails to obtain the correct values while the local density approximation (LDA) method successfully reproduces the experimental bulk modulus of ZrW2O8. Our calculated values of the shear and Young's moduli, Poisson's ratio, and Debye temperature of alpha-ZrW2O8 with LDA method are also in good agreement with the experimental results. Finally, we predict and analyze the optical properties of this material.
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| 35. |
- Ramzan, Muhammad, et al.
(författare)
-
High pressure phase determination and electronic properties of lithiumamidoborane
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:11, s. 111902-
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Tidskriftsartikel (refereegranskat)abstract
- In this study we report on the high pressure phase of the promising hydrogen storage material lithiumamidoborane (LiNH 2 BH 3), on the basis of density functional theory calculations with generalized gradient approximation. We take the five possible candidate structures, Pbca, Pbcn, Pcca, Pnma, and Pnnm for the high pressure study of LiNH 2 BH 3. The corresponding structures are relaxed with respect to fractional atomic coordinates and cell parameters, with the use of fully self-consistent ab initio electronic structure calculations to get the equilibrium parameters and total energies. Then we compare the energies of these phases and find that Pbcn is the most favorable phase at ≈100 GPa. Then we calculate the structural parameters of this phase. Finally, we calculate the density of states, Bader charge analysis, and corresponding electron density of this phase.
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| 36. |
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| 37. |
- Ramzan, Muhammad, et al.
(författare)
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Hybrid density functional and molecular dynamics study of promising hydrogen storage materials : Double metal amidoboranes and metal amidoborane ammoniates
- 2012
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:33, s. 17351-17359
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the recently synthesized materials, Na2Mg-(NH 2BH 3) 4, NaLi(NH 2BH 3) 2, Mg(NH 2BH 3) 2·NH 3, and Ca-(NH 2BH 3) 2·2NH 3, are studied, which were found suitable for hydrogen storage applications. The hybrid density exchange-correlation functional is employed to explore the structural and electronic properties of these materials using the first-principles method on the basis of density functional theory calculations. From the detailed study of electronic structures, it is found that the mixed cation amidoboranes and [NH 3] molecules play an important role in the dehydrogenation process. Bader charge analysis is performed to show the charge distribution between the constituent atoms. The corresponding electron densities and related properties of these compounds are also calculated. Furthermore, ab initio molecular dynamics simulations are performed to study the diffusion of hydrogen in these compounds, which consist of boron, nitrogen, and hydrogen atoms. The common features of these compounds are also revealed by explaining the electronic properties. Finally, it is shown that the mobility of hydrogen in Na 2Mg(NH 2BH 3) 4 and NaLi(NH 2BH 3) 2 is slightly higher than that in Mg(NH 2BH 3) 2·NH 3 and Ca(NH 2BH 3) 2·2NH 3 at the same temperatures.
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| 38. |
- Ramzan, Muhammad, 1971-, et al.
(författare)
-
Hybrid Density Functional Calculations and Molecular Dynamics Study of Lithium Fluorosulphate, A Cathode Material for Lithium-Ion Batteries
- 2011
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:5, s. 2600-2603
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we use hybrid density functional theory to calculate the electronic structure of lithium fluorosulphate (LiFeSO4F), which has been found recently to be an excellent cathode material for lithium-ion,batteries by Recham et al. (Nat. Mater. 2010, 9, 68). We calculate the average intercalation voltage of the corresponding battery, and we also analyze the electron charge distribution through Bader's analysis. Our results are in good agreement with the available experimental values. Then we studied the Li-diffusion in lithium fluorosulphate with ab initio molecular dynamics and found it to be three-dimensional.
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| 39. |
- Ramzan, Muhammad, et al.
(författare)
-
Hybrid exchange-correlation functional study of the structural, electronic, and mechanical properties of the MAX phases
- 2011
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 98:2, s. 021902-
-
Tidskriftsartikel (refereegranskat)abstract
- In this letter, we report on our results obtained with the hybrid functional HSE06 on the structural, electronic, and mechanical properties of the MAX phases. As a sample, we choose Ti2AlN, Ti2AlC, V2AlC, Nb2AlC, Ta2AlC, V2GeC, Ti3SiC2, and Ti4AlN3, which cover all the known types of MAX phases. From our calculations, we have found that V2GeC has the magnetically ordered ground state. Our results are compared to available experimental data, and it is shown that the HSE06 functional can be used as a predictive tool to study the properties of this family of compounds.
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| 40. |
- Ramzan, Muhammad, et al.
(författare)
-
Hydrogen diffusion in bulk and nanoclusters of MgH2 and the role of catalysts on the basis of ab initio molecular dynamics
- 2009
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:22
-
Tidskriftsartikel (refereegranskat)abstract
- We present ab initio molecular dynamics calculations based on density functional theory to study the hydrogen-deuterium exchange in bulk and nanoclusters of MgH2. Our calculations reveal the important role of catalysts to diffuse the hydrogen at low temperatures and increase the diffusion rate. We determine the diffusion constants, < D > of deuterium, and show the single hydrogen-deuterium exchange in bulk and nanocluster of MgH2. Our calculated value of diffusion constant of deuterium in bulk MgH2 is in excellent agreement with the experimental value. Furthermore, we show the edge site importance of catalysts in the fast diffusion of hydrogen.
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| 41. |
- Ramzan, Muhammad, et al.
(författare)
-
M(N+1)AX(N)(M=Ti,A=Al,X=H) phase class materials with hydrogen : Ti4AlH3 and Ti3AlH2
- 2010
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 96:26, s. 261906-
-
Tidskriftsartikel (refereegranskat)abstract
- To date more than 50 MAX phases known to exist but all of those are consist of nitrides or carbides. We present a modified type of these phases, Ti4AlH3 and Ti3AlH2, having hydrides in their composition, by our density functional theory (DFT) calculations. We study the structural stability, electronic structure, elastic, thermal, and mechanical properties of these materials which are comparable with well known phases: Ti3SiC2, Ti4AlN3, and Ti3AlC2. Moreover, these materials can also be studied for hydrogen storage purposes. We hope that our work will be helpful to discover the other types of such phases which are important from the technological and industrial point of view. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3459960]
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| 42. |
- Ramzan, Muhammad, 1971-, et al.
(författare)
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Molecular dynamics study of amorphous Ga-doped In2O3 : A promising material for phase change memory devices
- 2013
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:7, s. 072113-
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we employ the ab-initio molecular dynamics simulations, within the framework of density functional theory, to construct and characterize the amorphous structure of gallium-doped indium oxide. The electronic properties of amorphous and crystalline structures of Ga:In2O3 are investigated and compared by calculating the density of states, radial distribution function, bond angle distribution, and Bader charge analysis. We observe the band gap closure in amorphous structure, which corresponds to semiconductor to metallic transition in this material on amorphization. Our calculated results show the same characteristics of Ga:In2O3 with other phase change memory (PCM) materials available in literature and suggest it a promising candidate for PCM devices.
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| 43. |
- Ramzan, Muhammad, et al.
(författare)
-
Role of correlation effects in the superconducting material : InV6S8
- 2011
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 99:22, s. 221904-
-
Tidskriftsartikel (refereegranskat)abstract
- In this letter, we present the high pressure studies to compute the structural parameters and electronic structure of InV(6)S(8), using the first principles density functional theory (DFT) and DFT+U methods. While LDA and GGA fail to give the correct electronic and structural properties, the DFT+U method performs well to reproduce the experimental observed quantities of InV(6)S(8). We analyze the electronic structures and nesting of InV(6)S(8) at different pressure values and show that the nesting of energy bands reduces with compression. Finally, we conclude that the Hubbard like correction is necessary to take into account the correlation effects, which are very important in the correct description of InV(6)S(8), by choosing the moderate value of U.
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| 44. |
- Ramzan, Muhammad, et al.
(författare)
-
Structural and energetic analysis of the hydrogen storage materials LiNH2BH3 and NaNH2BH3 from ab initio calculations
- 2009
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 79:13
-
Tidskriftsartikel (refereegranskat)abstract
- Ammonia borane (NH3BH3) possesses many appealing properties as a hydrogen storage material; however, the release of trace amounts of borazine during the desorption process is troublesome. Recently, it was found that substitution of one of the H atoms in the NH3 group by Li or Na could significantly improve the hydrogen desorption properties. The resulting lithium amidoborane (LiNH2BH3) and sodium amidoborane (NaNH2BH3) compounds have been studied by us using density-functional theory. Specifically, we have succeeded in determining the detailed crystal structures of LiNH2BH3 and NaNH2BH3, including the atomic positions in their respective unit cells. Calculated hydrogen removal energies of the hydrogen release reactions are found to be in good agreement with the experimental trend.
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| 45. |
- Ramzan, Muhammad
(författare)
-
Structural, Electronic and Mechanical Properties of Advanced Functional Materials
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The search for alternate and renewable energy resources as well as the efficient use of energy and development of such systems that can help to save the energy consumption is needed because of exponential growth in world population, limited conventional fossil fuel resources, and to meet the increasing demand of clean and environment friendly substitutes. Hydrogen being the simplest, most abundant and clean energy carrier has the potential to fulfill some of these requirements provided the development of efficient, safe and durable systems for its production, storage and usage.Chemical hydrides, complex hydrides and nanomaterials, where the hydrogen is either chemically bonded to the metal ions or physiosorbed, are the possible means to overcome the difficulties associated with the storage and usage of hydrogen at favorable conditions. We have studied the structural and electronic properties of some of the chemical hydrides, complex hydrides and functionalized nanostructures to understand the kinetics and thermodynamics of these materials.Another active field relating to energy storage is rechargeable batteries. We have studied the detailed crystal and electronic structures of Li and Mg based cathode materials and calculated the average intercalation voltage of the corresponding batteries. We found that transition metal doped MgH2 nanocluster is a material to use efficiently not only in batteries but also in fuel-cell technologies.MAX phases can be used to develop the systems to save the energy consumption. We have chosen one compound from each of all known types of MAX phases and analyzed the structural, electronic, and mechanical properties using the hybrid functional. We suggest that the proper treatment of correlation effects is important for the correct description of Cr2AlC and Cr2GeC by the good choice of Hubbard 'U' in DFT+U method.Hydrogen is fascinating to physicists due to predicted possibility of metallization and high temperature superconductivity. On the basis of our ab initio molecular dynamics studies, we propose that the recent claim of conductive hydrogen by experiments might be explained by the diffusion of hydrogen at relevant pressure and temperature.In this thesis we also present the studies of phase change memory materials, oxides and amorphization of oxide materials, spintronics and sulfide materials.
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| 46. |
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| 47. |
- Ramzan, Muhammad, et al.
(författare)
-
Transition metal doped MgH2 : A material to potentially combine fuel-cell and battery technologies
- 2010
-
Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 35:19, s. 10373-10376
-
Tidskriftsartikel (refereegranskat)abstract
- MgH2 is studied as a negative electrode material for rechargeable batteries on the basis of density functional theory calculations. We calculate the average voltage of the corresponding Li-ion battery, which is in good agreement with the experimental value, and we predict the average voltage for the Na-ion battery. Then, molecular dynamics simulations are used to study the diffusive properties of lithium in MgH2 clusters. In particular, we dope MgH2 with transition metals (Fe, Ni, Ti, and V), and analyze the effect on the diffusion of lithium, which is shown to be essentially unaffected. Therefore, we propose that transition metal doped MgH2 is a material that can be used efficiently in both batteries and fuel-cell technologies.
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| 48. |
- Rashad, Ramzan, 1971-, et al.
(författare)
-
On-chip BIST for radio front-ends.
- 2006
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Ingår i: Swedish system-on-chip conference.,2006. - Lund : Lunds universitet.
-
Konferensbidrag (refereegranskat)
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| 49. |
- Sagynbaeva, Myskal, et al.
(författare)
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Tweaking the magnetism of MoS2 nanoribbon with hydrogen and carbon passivation
- 2014
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 25:16, s. 165703-
-
Tidskriftsartikel (refereegranskat)abstract
- Using density functional theory (DFT), we report the modulated electronic and magnetic properties of MoS2 nanoribbon by passivating the ribbon edges with H and C separately. For the modeled symmetric MoS2 nanoribbon with a zig-zag type edge, one side is terminated at Mo and the other side is terminated at S. For the zig-zag type, we have studied two ribbons of width similar to 3 angstrom and 6 angstrom respectively. Both of these pristine zig-zag type nanoribbons are found to be metallic and also ferromagnetic. However, the increase in the ribbon width results in a decrease in the net magnetic moment of the nanoribbon. Thereafter, we study the modulated electronic and magnetic properties of the nanoribbon of similar to 3 angstrom width by saturating the ribbon edges with H and C. In one case, by passivating the zig-zag type ribbon with H at the S terminated edge, we find a net increase in magnetic moment of the ribbon when compared with the pristine one. Furthermore, when the ribbon is passivated with H at both of the edges, the net magnetic moment shows a decreasing trend. In another case, the zig-zag nanoribbon is passivated with C in a similar fashion to H and we find with one edge passivation the net magnetic moment of the ribbon decreases, whereas with both edges C passivated the ribbon magnetism increases significantly. However, the nanoribbon modeled with the armchair type of edge and terminated with Mo at both sides is found to be non-magnetic and semiconducting. Passivating the armchair type nanoribbon with H and C, we find the band gap shows an increasing trend when going from one side to both sides passivation. In all cases, the armchair type nanoribbons show non-magnetic behavior.
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| 50. |
- Siddiqui, Amna Jabbar, et al.
(författare)
-
Serum metallomics reveals insights into the associations of elements with the progression of preleukemic diseases toward acute leukemia
- 2024
-
Ingår i: Biology Methods and Protocols. - : Oxford University Press. - 2396-8923. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- Acute leukemia (AL) is a critical neoplasm of white blood cells with two main subtypes: acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). This study is focused on understanding the association of the preleukemic disease aplastic anemia (APA) with ALL and AML at metallomic level, using healthy subjects as a control. In this study, a validated and efficient inductively coupled plasma-mass spectrometry/MS-based workflow was employed to profile a total of 13 metallomic features. The study encompassed 41 patients with AML, 62 patients with ALL, 46 patients with APA, and 55 age-matched healthy controls. The metallomic features consisted of eight essential elements (Ca, Co, Cu, Fe, Mg, Mn, Se, and Zn) and five non-essential/toxic elements (Ag, Cd, Cr, Ni, and Pb). Six out of the 13 elements were found to be substantially different (P < .05) using absolute concentrations between serum samples of AL (ALL and AML) and preleukemia (APA) patients in comparison with healthy subjects. Elements including magnesium, calcium, iron, copper, and zinc were upregulated and only one element (chromium) was downregulated in serum samples of disease when compared with healthy subjects. Through the utilization of both univariate tests and multivariate classification modeling, it was determined that chromium exhibited a progressive behavior among the studied elements. Specifically, chromium displayed a sequential upregulation from healthy individuals to preleukemic disease (APA), and ultimately in patients diagnosed with ALL. Overall, metallomic-based biomarkers may have the utility to predict the association of APA with ALL.
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