| 1. |
|
|
| 2. |
- Chowdhury, Suman, et al.
(författare)
-
A real-space study of random extended defects in solids : Application to disordered Stone–Wales defects in graphene
- 2014
-
Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier BV. - 1386-9477 .- 1873-1759. ; 61:0, s. 191-197
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract We propose here a first-principles, parameter free, real space method for the study of disordered extended defects in solids. We shall illustrate the power of the technique with an application to graphene sheets with randomly placed Stone–Wales defects and shall examine the signature of such random defects on the density of states as a function of their concentration. The technique is general enough to be applied to a whole class of systems with lattice translational symmetry broken not only locally but by extended defects and defect clusters. The real space approach will allow us to distinguish signatures of specific defects and defect clusters.
|
|
| 3. |
- Datta, S., et al.
(författare)
-
Structure, bonding, and magnetism of cobalt clusters from first-principles calculations
- 2007
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 76:1, s. 014429-
-
Tidskriftsartikel (refereegranskat)abstract
- The structural, electronic, and magnetic properties of Co-n clusters (n=2-20) have been investigated using density functional theory within the pseudopotential plane wave method. An unusual hexagonal growth pattern has been observed in the intermediate size range, n=15-20. The cobalt atoms are ferromagnetically ordered and the calculated magnetic moments are found to be higher than that of corresponding hcp bulk value, which are in good agreement with the recent Stern-Gerlach experiments. The average coordination number is found to dominate over the average bond length to determine the effective hybridization and consequently the cluster magnetic moment.
|
|
| 4. |
- Ganguli, Nirmal, et al.
(författare)
-
Electronic structure and magnetism of transition metal doped Zn12O12 clusters : Role of defects
- 2010
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 108:12, s. 123911-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive study of the energetics and magnetic properties of ZnO clusters doped with 3d transition metals (TMs) using ab initio density functional calculations in the framework of generalized gradient approximation + Hubbard U (GGA+U) method. Our results within GGA+U for all 3d dopants except Ti indicate that antiferromagnetic interaction dominates in a neutral, defect-free cluster. Formation energies are calculated to identify the stable defects in the ZnO cluster. We have analyzed in details the role of these defects to stabilize ferromagnetism when the cluster is doped with Mn, Fe, and Co. Our calculations reveal that in the presence of charged defects the TM atoms residing at the surface of the cluster may have an unusual oxidation state, that plays an important role to render the cluster ferromagnetic. Defect induced magnetism in ZnO clusters without any TM dopants is also analyzed. These results on ZnO clusters may have significant contributions in the nanoengineering of defects to achieve desired ferromagnetic properties for spintronic applications.
|
|
| 5. |
- Ganguli, Nirmal, et al.
(författare)
-
The making of ferromagnetic Fe doped ZnO nanoclusters
- 2009
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:19, s. 192503-
-
Tidskriftsartikel (refereegranskat)abstract
- In this letter, the authors present a study of the energetics and magnetic interactions in Fe doped ZnO clusters by ab initio density functional calculations. The results indicate that defects under suitable conditions can induce ferromagnetic interactions between the dopant Fe atoms whereas antiferromagnetic coupling dominates in a neutral defect-free cluster. The calculations also reveal an unusual ionic state of the dopant Fe atom residing at the surface of the cluster, a feature that is important to render the cluster ferromagnetic.
|
|
| 6. |
|
|
| 7. |
- Panda, Swarup K., et al.
(författare)
-
Electronic structure and exchange interactions of insulating double perovskite La2CuRuO6
- 2016
-
Ingår i: PHYSICAL REVIEW B. - 2469-9950. ; 94:6
-
Tidskriftsartikel (refereegranskat)abstract
- We have performed first-principles calculations of the electronic and magnetic properties of insulating double perovskite compound La2CuRuO6 (LCRO) which has recently been reported to exhibit intriguing magnetic properties. We derived a tight-binding Hamiltonian for LCRO based on the Nth-order muffin-tin orbital (NMTO) downfolding technique. The computed on-site energies and hopping integrals are used to estimate the dominant exchange interactions employing an extended Kugel-Khomskii model. This way the dominant exchange paths were identified and a low-energy spin model was proposed. The Green function method based on the magnetic force theorem has also been used to extract the exchange interactions to provide a more accurate estimation and to justify the model calculations. Our results show that the nearest neighbor (NN) Cu-Ru magnetic interactions are very much direction dependent and a strong antiferromagnetic next nearest neighbor Ru-Ru interaction along the crystallographic b axis is responsible for the magnetic frustration observed experimentally in this system. We argue that due to the broken symmetry, NN Cu-Ru interaction becomes stronger along one direction than the other, which essentially reduces the amount of frustration and helps the system to achieve an antiferromagnetic ground state at low temperature. A detailed microscopic explanation of the exchange mechanism is discussed. We also find that spin-orbit coupling effect is significant and causes a canting of the Ru spin with respect to the Cu moments.
|
|
| 8. |
- Patel, Ami V, et al.
(författare)
-
Fatty acid synthase is a metabolic oncogene targetable in malignant peripheral nerve sheath tumors
- 2015
-
Ingår i: Neuro-Oncology. - : Oxford University Press (OUP). - 1522-8517 .- 1523-5866. ; 17:12, s. 1599-1608
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas with minimal therapeutic opportunities. We observed that lipid droplets (LDs) accumulate in human MPNST cell lines and in primary human tumor samples. The goal of this study was to investigate the relevance of lipid metabolism to MPNST survival and as a possible therapeutic target.METHODS: Based on preliminary findings that MPNSTs accumulate LDs, we hypothesized that a deregulated lipid metabolism supports MPNST cell survival/proliferation rate. To test this, we examined respiration, role of fatty acid oxidation (FAO), and the enzyme fatty acid synthase involved in de novo fatty acid synthesis in MPNSTs using both genetic and pharmacological tools.RESULTS: We demonstrate that LDs accumulate in MPNST cell lines, primary human and mouse MPNST tumors, and neural crest cells. LDs from MPNST cells disappear on lipid deprivation, indicating that LDs can be oxidized as a source of energy. Inhibition of FAO decreased oxygen consumption and reduced MPNST survival, indicating that MPNST cells likely metabolize LDs through active FAO. FAO inhibition reduced oxygen consumption and survival even in the absence of exogenous lipids, indicating that lipids synthesized de novo can also be oxidized. Consequently, inhibition of de novo fatty acid synthesis, which is overexpressed in human MPNST cell lines, effectively reduced MPNST survival and delayed induction of tumor growth in vivo.CONCLUSION: Our results show that MPNSTs depend on lipid metabolic pathways and suggest that disrupting lipid metabolism could be a potential new strategy for the development of MPNST therapeutics.
|
|
| 9. |
- Sanyal, Biplab, et al.
(författare)
-
Ferromagnetism in Mn doped half-Heusler NiTiSn : Theory and experiment
- 2006
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:21, s. 212502-
-
Tidskriftsartikel (refereegranskat)abstract
- In this letter, the authors show by ab initio density functional calculations and experiments that Mn doped semiconducting half-Heusler compound NiTiSn can exhibit room-temperature ferromagnetism. Curie temperatures were calculated by Monte Carlo simulations using calculated Heisenberg exchange parameters in an ab initio Green's function approach. The calculated temperature exceeds room temperature for a Mn doping concentration of 22%. Magnetic measurements confirm the presence of possible intrinsic ferromagnetism in these systems. This brings up the possibility of considering this system as a potential candidate for use in room-temperature spintronic devices.
|
|
