| 1. |
- Araujo, Carlos Moyses, et al.
(författare)
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Electronic and optical properties of MgH2: a first-principle GW investigation
- 2005
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Ingår i: Journal of Applied Physics. - 0021-8979. ; 98:9, s. 096106
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of MgH2 is studied using the state of the art all-electron projector-augmented-wave GW approximation. Both the ground-state and the high-pressure transformations are considered in this investigation. We have found an indirect (direct) band-gap of 5.58 eV (6.52 eV) for α-MgH2, which has a good agreement with the experimental findings. For the γ- and β-phases, we have found indirect (direct) band-gap values of 5.24 eV (5.33 eV) and 3.90 eV (4.72 eV), respectively. The optical properties are investigated by means of the complex dielectric function, which is calculated within the framework of a full-potential linearized augmented plane wave method and corrected by scissor operators. All phases are found to be color neutral insulators.
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| 2. |
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| 3. |
- Kim, Duck Young, et al.
(författare)
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Crystal structure of the pressure-induced metallic phase of SiH4 from ab initio theory
- 2008
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - 0027-8424. ; 105:43, s. 16454-16459
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Tidskriftsartikel (refereegranskat)abstract
- Metallization of pure solid hydrogen is of great interest, not least because it could lead to high-temperature superconductivity, but it continues to be an elusive goal because of great experimental challenges. Hydrogen-rich materials, in particular, CH4, SiH4, and GeH4, provide an opportunity to study related phenomena at experimentally achievable pressures, and they too are expected to be high-temperature superconductors. Recently, the emergence of a metallic phase has been observed in silane for pressures just above 60 GPa. However, some uncertainty exists about the crystal structure of the discovered metallic phase. Here, we show by way of elimination, that a single structure that possesses all of the required characteristics of the experimentally observed metallic phase of silane from a pool of plausible candidates can be identified. Our density functional theory and GW calculations show that a structure with space group P4/nbm is metallic at pressures > 60 GPa. Based on phonon calculations, we furthermore demonstrate that the P4/nbm structure is dynamically stable at > 43 GPa and becomes the ground state at 97 GPa when zero-point energy contributions are considered. These findings could lead the way for further theoretical analysis of metallic phases of hydrogen-rich materials and stimulate experimental studies.
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| 4. |
- Kim, D. Y., et al.
(författare)
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Structurally induced insulator-metal transition in solid oxygen : A quasiparticle investigation
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 77:9, s. 092104
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Tidskriftsartikel (refereegranskat)abstract
- Structural phase transition of solid oxygen has been investigated by using ab initio calculations based on density functional theory. We found sudden jumps in structural parameters at the transition pressure, which confirm that the epsilon (epsilon) phase undergoes a first-order isostructural phase transformation to the zeta (zeta) phase. In particular, this happens without any molecular dissociation. Using the GW approximation to calculate the band-gap closure under high pressure, we show that the structural transition is accompanied by an insulator-metal transition, contrary to a standard density functional calculation which predicts a metallization at a much lower pressure in the epsilon phase.
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| 5. |
- Lebègue, Sébastien, et al.
(författare)
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Quasiparticle and optical properties of BeH2
- 2007
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Ingår i: Journal of Physics : Condensed Matter. - 0953-8984. ; 19:3, s. 036223
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Tidskriftsartikel (refereegranskat)abstract
- The quasiparticle and optical properties of BeH2 are computed by means of the all-electron GW approximation in conjunction with the projector augmented wave (PAW) method. The GW approximation, through the calculation of the self-energy and the optical dielectric function in the random phase approximation, shows that BeH2 is a large band gap insulator. The results are discussed in view of future experiments.
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| 6. |
- Scheicher, Ralph H., et al.
(författare)
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Cubic metallic phase of aluminum hydride showing improved hydrogen desorption
- 2008
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Ingår i: Applied Physics Letters. - 0003-6951. ; 92:20, s. 201903
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Tidskriftsartikel (refereegranskat)abstract
- Wereport on our results calculated from density functional theory andGW of the dehydrogenation properties in a cubic phase ofAlH3. The metallic nature of the electronic structure entails amore favorable hydrogen removal energy which is lowered by 75%compared to the insulating hexagonal phase. This remarkable reduction inthe Al–H bond strength bears important consequences for feasible applicationsof AlH3 as an on-board hydrogen storage material for mobileapplications. We suggest that the cubic phase could be preparedand stabilized experimentally at ambient pressure by off-board quenching.
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