| 1. |
- Jamwal, Prarena, et al.
(författare)
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Enhancement of superconductivity in Zr2S2C arising from phonon softening on transition from bulk to monolayer
- 2024
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 36:38
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Tidskriftsartikel (refereegranskat)abstract
- We report a new compound, Zr2S2C, belonging to the transition metal carbo-chalcogenide (TMCC) family. Through first-principles calculations, our analysis of phonon dispersion spectra indicates that the compound is dynamically stable in both bulk and monolayer forms. We systematically investigated the electronic structure, phonon dispersion, and electron-phonon coupling (EPC) driven superconducting properties in bulk and monolayer Zr2S2C. The results demonstrate the metallic character of bulk Zr2S2C, with a weak EPC strength (lambda) of 0.41 and superconducting critical temperature (Tc) of similar to 3 K. The monolayer Zr2S2C has an enhanced lambda of 0.62 andTcof similar to 6.4 K. The increased lambda value in the monolayer results from the softening of the acoustic phonon mode. We found that when biaxial strain is applied, the low energy acoustic phonon mode in monolayer becomes even softer. This softening leads to a transformation of the Zr2S2C monolayer from its initial weak coupling state (lambda= 0.62) to a strongly coupled state, resulting in an increased lambda value of 1.33. Consequently, the superconducting critical temperature experiences a twofold increase. These findings provide a theoretical framework for further exploration of the layered two-dimensional TMCC family, in addition to offering valuable insights.
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| 2. |
- Jamwal, Prarena, et al.
(författare)
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Van Hove singularity driven enhancement of superconductivity in two-dimensional tungsten monofluoride (WF)
- 2024
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 36:24
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Tidskriftsartikel (refereegranskat)abstract
- Superconductivity in two-dimensional materials has gained significant attention in the last few years. In this work, we report phonon-mediated superconductivity investigations in monolayer Tungsten monofluoride (WF) by solving anisotropic Migdal Eliashberg equations as implemented in EPW. By employing first-principles calculations, our examination of phonon dispersion spectra suggests that WF is dynamically stable. Our results show that WF has weak electron–phonon coupling (EPC) strength (λ) of 0.49 with superconducting transition temperature (Tc) of 2.6 K. A saddle point is observed at 0.11 eV below the Fermi level (EF) of WF, which corresponds to the Van Hove singularity (VHS). On shifting the Fermi level to the VHS by hole doping (3.7 × 1014 cm−2), the EPC strength increases to 0.93, which leads to an increase in the Tc to 11 K. However, the superconducting transition temperature of both pristine and doped WF increases to approximately 7.2 K and 17.2 K, respectively, by applying the Full Bandwidth (FBW) anisotropic Migdal–Eliashberg equations. Our results provide a platform for the experimental realization of superconductivity in WF and enhancement of the superconducting transition temperature by adjusting the position of EF to the VHS.
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| 3. |
- Kagdada, Hardik L., et al.
(författare)
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Exploring A-Site Cation Variations in Dion-Jacobson Two-Dimensional Halide Perovskites for Enhanced Solar Cell Applications : A Density Functional Theory Study
- 2024
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Ingår i: Advanced Energy & Sustainability Research. - : Wiley-VCH Verlagsgesellschaft. - 2699-9412. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- The exceptional photophysical and electronic properties of 2D hybrid perovskites possess potential applications in the field of solar energy harvesting. The present work focuses on the two systems, exhibiting the Dion–Jacobson phase of 2D perovskite consisting of methylammonium (MA) and formamidinium (FA) cations at A-site and 3-(aminomethyl)pyridinium (3AMPY) as ring-shaped organic spacer. Altering A-site cations creates a distortion of inorganic layers and hydrogen bond interactions. It has been noted that the angles of Pb–I–Pb and I–Pb–I are more symmetric (close to 180°) for (3AMPY)(MA)Pb2I7 compared to (3AMPY)(FA)Pb2I7 and result in increase of bandgap from 1.51 to 1.58 eV. This further leads to a significant difference in Rashba splitting energy under the influence of spin-orbit coupling effects, where the highest splitting (36 meV) is calculated for conduction band edge of the (3AMPY)(FA)Pb2I7, suggesting the promising applications toward spintronics. The calculated absorption spectra cover the range from 300 to 450 nm, indicating significant optical activity of 2D (3AMPY)(MA)Pb2I7 and (3AMPY)(FA)Pb2I7 in the visible and ultraviolet regions, which bodes well for their application in advanced optoelectronic devices. The bandgap and high absorption coefficients present more than 30% of theoretical power conversion efficiency for both systems, as calculated from the spectroscopic-limited maximum efficiency.
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| 4. |
- Khossossi, Nabil, et al.
(författare)
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Unveiling the catalytic potential of two-dimensional boron nitride in lithium-sulfur batteries
- 2024
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Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 479
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-sulfur (Li-S) batteries, renowned for their potential high energy density, have attracted attention due to their use of earth-abundant elements. However, a significant challenge lies in developing suitable materials for both lithium-based anodes, which are less prone to lithium dendrite formation, and sulfur-based cathodes. This obstacle has hindered their widespread commercial viability. In this study, we present a novel sulfur host material in the form of a two-dimensional semiconductor boron nitride framework, specifically the 2D orthorhombic diboron dinitride (o-B2N2). The inherent conductivity of o-B2N2 mitigates the insulating nature often observed in sulfur-based electrodes. Notably, the o-B2N2 surface demonstrates a high binding affinity for long-chain Li-polysulfides, leading to a significant reduction in their dissolution into the DME/DOL electrolytes. Furthermore, the preferential deposition of Li2S on the o-B2N2 surface expedites the kinetics of the lithium polysulfide redox reactions. Additionally, our investigations have revealed a catalytic mechanism on the o-B2N2 surface, significantly reducing the free energy barriers for various sulfur reduction reactions. Consequently, the integration of o-B2N2 as a host cathode material for Li-S batteries holds great promise in suppressing the shuttle effect of lithium polysulfides and ultimately enhancing the overall battery performance. This represents a practical advancement for the application of Li-S batteries.
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| 5. |
- Kibbou, Moussa, et al.
(författare)
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Advancing photovoltaics and optoelectronics : Exploring the superior performance of lead-free halide perovskites
- 2024
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Ingår i: Optical materials (Amsterdam). - : Elsevier. - 0925-3467 .- 1873-1252. ; 147
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Tidskriftsartikel (refereegranskat)abstract
- One of the emerging directions that has greatly advanced the fields of photovoltaics and optoelectronics is the development of lead-free inorganic halide perovskites. In this study, ab-initio methods were employed to forecast the structural, electronic, and optical behavior of the perovskite materials Cs2Cu+Al3+X6 (where X represents Cl or Br). The analyses conducted have revealed the exceptional structural characteristics of these compounds. The electronic band structure and density of states were computed using the PBE method with the mBJ potential. The direct bandgaps of Cs2CuAlCl6 and Cs(2)CuAlBr(6 )were determined to be 1.35 eV and 0.93 eV, respectively. This suitable electrical bandgap results in high visible-light absorption. As a result, the optical characteristics exhibit a significant absorption coefficient (alpha(omega) approximate to 1.1 x 10(5) cm(-1) for Cs2CuAlBr6 and 0.77 x10(5) cm(-1) for Cs2CuAlCl6), substantial conductivity, and negligible reflectivity (R(omega) < 10%). These attributes render Cs(2)CuAlCl(6 )and Cs2CuAlBr6 semiconductors highly appealing for optoelectronic applications. The maximum spectral light conversion efficiency under AM1.5G solar irradiation was assessed by altering the thickness of the structures. The results reveal that the chlorinated perovskite achieves a slightly higher efficiency of 32.72%, whereas the brominated perovskite reaches an efficiency of 29.31%. Despite their remarkably advantageous bandgaps, limited reflectivity, and impressive efficiency, environmentally friendly halide perovskite compounds hold promise as renewable energy conversion materials. This suggests the potential for substantial enhancements in solar cell performance. Furthermore, employing the finite element (FE) method, we performed calculations to assess carrier generation within a specially engineered solar cell structure comprising an environmentally friendly multilayer (CH3NH3SnI3 and Cs2CuAlX6). Our discoveries unveiled an exceptionally elevated total generation rate at the interfaces between CH3NH3SnI3 and Cs2CuAlX6, reaching approximately 2.5 x 10(29) m(-3)/s. These findings offer novel perspectives that contribute to the research community and hold the potential to advance future solar cell systems.
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| 6. |
- Kotmool, Komsilp, et al.
(författare)
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Novel hard and unusual superconducting monoclinic phase of FeB2C2 : An ab initio evolutionary study
- 2024
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 135:22
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on conducting an ab initio evolutionary investigation to search for stable polymorphs of iron diborocarbides with the formula FeB2C2. We also examined other forms of C contents, including FeB3C and FeBC3. Our findings reveal that the lowest energetic structure of FeB2C2 is a semimetallic monoclinic phase with a space group (s.g.) of C2/m and a metastable metallic phase of FeB2C2 is an orthorhombic structure with s.g. of Pmmm. In addition, structural and relative properties of FeB3C and FeBC3 are performed and discussed to compare with FeB2C2. All predicted structures are dynamically and elastically stable, verified without negative phonon frequency and Born criteria, respectively. We also analyzed the energetic stability through calculated cohesive and formation energies, which showed that C2/m- FeB2C2 is stable at low pressure. Interestingly, the C2/m and Pmmm phases of FeB2C2 are hard materials with Vickers hardness (Hv) of 22.40 and 27.52 GPa, respectively. Additionally, we examined the electron-phonon coupling of both FeB2C2 phases. Unexpectedly, we found that the semimetallic C2/m-FeB2C2 phase is a superconductor with a significant superconducting temperature (Tc) exceeding 6 K. These findings provide some novel results for the Fe-B-C system and pave the way for investigating other metal borocarbides and related ternary compounds.
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| 7. |
- Kotmool, Komsilp, et al.
(författare)
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Stability, thermodynamic, electronic, and thermoelectric properties of triclinic Cu2Se structure
- 2024
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 50:11 Part A, s. 19060-19066
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Tidskriftsartikel (refereegranskat)abstract
- The conversion of heat into electricity using the thermoelectric effect is a crucial issue to tackle the ever-increasing global energy consumption. Cu2Se is one of the high-performance thermoelectric materials due to its liquid-like atomic structure, which minimizes the phonon-derived thermal conductivity. Nevertheless, the unambiguous atomic structure of the low-temperature phase, α-Cu2Se, remains controversial. By employing a combination of theoretical approaches including an evolutionary algorithm for structural searching, density functional theory, and lattice dynamics, the α-Cu2Se phase is proposed to crystalize in the dynamically stable triclinic Cu2Se structure (s.g. P1) which can be regarded as a monoclinic polymorph (s.g. P21/c(dagger)) through slight distortion. The corresponding heat capacity (CV) and Debye temperature (ΘD) are 0.37 J/gK and 276 K, respectively, indicating low thermal conductivity in the material. The semiconducting P1 phase possesses an indirect gap of 1.0 eV. Additionally, based on the Boltzmann transportation theory, fundamental thermoelectric parameters around the transition temperature (300-500 K) are investigated. Beyond the semiconducting phase, a novel metallic phase identified as the triclinic P1(over bar) phase is also discovered, exhibiting a two-dimensional (2D) crystal geometry.
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| 8. |
- Kumar, Vipin, et al.
(författare)
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Anisotropic properties of two-dimensional (2D) tin dihalide (SnX2, X = Cl, Br, I) monolayer binary materials
- 2024
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 36:11
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigated the electronic properties and photoresponse of two-dimensional SnX2 (X = Cl, Br, I) monolayer binary materials using computational techniques. The calculated band structure and density of states indicate that these are large band gap semiconducting materials with an indirect band gap. The studied chemical bonding mechanism shows the existence of the hybrid bonding of ionic and covalent bonds in these dihalide materials. The valence band (VB) and conduction band (CB) edge positions are also estimated, using the concept of electronegativity and band gap, to investigate the photocatalytic activity of SnX2. Next, we investigated the polarization and energy-dependent dielectric and optical functions along the crystallographic axes of these materials in the linear response approach of the perturbing incident oscillating light field. These materials exhibit an anisotropic behavior of these functions, especially in the high-energy visible and low-energy ultraviolet (UV) regions. The absorption of incident light photons is very fast in SnI2 than SnBr2 and SnCl2 in the low-energy UV region. It demonstrates the higher absorption coefficient and optical conductivity in Snl2. The obtained average static refractive index of SnCl2 is comparable to that of glass (1.5), showing its application as transparent material. The low reflection coefficient, less than 20%, makes them superior for antireflection coating materials in the infrared and visible regions. The prominent energy loss peaks show the existence of plasmon resonances in these materials. The most of losses occur in the UV region. The investigated electronic and photoresponse properties indicate that these Sn-based dihalide materials are excellent for electronic devices and optoelectronic applications. Also, the calculated VB and CB edge positions with respect to the normal hydrogen electrode show the favorable water-splitting capability of these materials.
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| 9. |
- Lahraichi, Hanane, et al.
(författare)
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Design of 2D half-metallic CoAl2S4 with robust ferromagnetism and high Curie temperature
- 2024
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier. - 0304-8853 .- 1873-4766. ; 599
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional 2D ferromagnetic materials featuring intrinsic half-metallicity (HM) and high critical temperature Tc emerge as promising candidates for innovative low-dimensional spintronic devices. In this study, we employ first-principles calculations to predict a novel 2D half-metallic ferromagnet CoAl2S4 monolayer, a member of the layered AB2X4 family. The material’s energetic, mechanical, and dynamical stability is affirmed through analyses of its cohesive energy, elastic constants, and phonon spectrum, respectively. The ferromagnetic behavior observed in CoAl2S4 can be explained by the superexchange interaction of Co-S-Co bonds, consistent with the Goodenough–Kanamori rules. Notably, CoAl2S4 displays robust ferromagnetism with a Curie temperature reaching up to 435 K. The band structures show a large half-metal gap (2.83eV), ensuring the stability of the half-metallic state. Additionally, the CoAl2S4 monolayer demonstrates a preferential easy magnetization along the out-of-plane direction. Consequently, the rich CoAl2S4 monolayer is expected to boost advancements in spintronics, magnetostrictive materials, and magnetic memory devices.
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| 10. |
- Lei, Chengan, et al.
(författare)
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Controllable dual-polarization valley physics in the strain-engineered 2D monolayer of VC2N4
- 2024
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 12:6, s. 2156-2164
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Tidskriftsartikel (refereegranskat)abstract
- Valley-related physics has garnered significant attention in fundamental studies and cutting-edge information technologies. However, such valleytronic materials have rarely been reported and suffer from in-plane magnetization. Herein, based on first-principles calculations and tight-binding model analysis, we identify the existence of intrinsic valley-contrasting physics in bipolar ferromagnetic monolayer VC2N4 with robust perpendicular magnetic anisotropy behavior. Valley polarization arises spontaneously due to the simultaneous presence of broken space- and time-inversion symmetries. Interestingly, valley polarization is remarkably observed in both the valence and conduction bands around the K/K′ valley due to large spin splitting, indicating rare dual-polarization valley features, which is advantageous for achieving the captivating anomalous valley Hall effect relied on the valley-contrasting Berry curvature. Remarkably, the valley polarization can be switched on/off by applying a moderate biaxial strain. Our work provides a competitive candidate for exploring valley-dependent physics and its applications in valleytronics.
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