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Ab initio studies on phase transition, thermoelastic, superconducting and thermodynamic properties of the compressed cubic phase of AlH3
Y. K. Wei; N. N. Ge; X. R. Chen; G. F. Ji; L. C. Cai; Z. W. Gu
2014
Source PublicationJournal of Applied Physics
ISSN0021-8979
Volume115Issue:12
AbstractThe phase transition, thermoelastic, lattice dynamic, and thermodynamic properties of the cubic metallic phase AlH3 were obtained within the density-function perturbation theory. The calculated elastic modulus and phonon dispersion curves under various pressures at 0K indicate the cubic phase is both mechanically and dynamically stable above 73 GPa. The superconducting transition temperature T-c was calculated using the Allen-Dynes modification of the McMillan formula based on BCS theory. The calculations show that T-c for the cubic phase AlH3 is 8.5K (mu* = 0.1) at the onset of this phase (73GPa), while decreases to 5.7K at 80GPa and almost disappears at 110GPa, consisting with experimental phenomenon that there was no superconducting transition observed down to 4K over a wide pressure range 110-164GPa. It is found that the soft phonon mode for branch 1, namely, the lowest acoustic mode, plays a crucial role in elevating the total EPC parameter lambda of cubic AlH3. And the evolution of T-c with pressure follows the corresponding change of this soft mode, i.e. this mode is responsible for the disappearance of T-c in experiments. Meanwhile, the softening of this lowest acoustic mode originates from the electronic momentum transfer from M to R point. This phenomenon provides an important insight into why drastic changes in the diffraction pattern were observed in the pressure range of 63-73GPa in Goncharenko's experiments. Specifically, once finite electronic temperature effects are included, we find that dynamical instabilities can be removed in the phonon dispersion for P >= 63GPa, rendering the metastability of this phase in the range of 63-73GPa, and T-c (15.4K) becomes remarkably high under the lowest possible pressure (63GPa) compared with that of under 73GPa (8.5K). Our calculations open the possibility that finite temperature may allow cubic AlH3 to be dynamically stabilized even for pressures below 73 GPa. It is reasonable to deduced that if special techniques, such as rapid decompression, quenching, and annealing, are implemented in experiments, higher T-c can be observed in hydrides or hydrogen-rich compounds under much lower pressure than ever before. (C) 2014 AIP Publishing LLC.
description.department[wei, yong-kai ; ge, ni-na ; chen, xiang-rong] sichuan univ, coll phys sci & technol, chengdu 610064, peoples r china. [wei, yong-kai ; ge, ni-na ; ji, guang-fu ; cai, ling-cang ; gu, zhuo-wei] china acad engn phys, inst fluid phys, natl key lab shock wave & detonat phys, mianyang 621900, peoples r china. [chen, xiang-rong] chinese acad sci, int ctr mat phys, shenyang 110016, peoples r china. ; chen, xr (reprint author), sichuan univ, coll phys sci & technol, chengdu 610064, peoples r china. ; xrchen@scu.edu.cn ; cyfjkf@caep.ac.cn
KeywordStrong-coupled Superconductors Rare-earth Trihydrides Aluminum-hydride Metal Hydrides Pressure-raman Temperature Hydrogen Polymorphs Dynamics Phonons
URL查看原文
Language英语
Document Type期刊论文
Identifierhttp://ir.imr.ac.cn/handle/321006/72929
Collection中国科学院金属研究所
Recommended Citation
GB/T 7714
Y. K. Wei,N. N. Ge,X. R. Chen,et al. Ab initio studies on phase transition, thermoelastic, superconducting and thermodynamic properties of the compressed cubic phase of AlH3[J]. Journal of Applied Physics,2014,115(12).
APA Y. K. Wei,N. N. Ge,X. R. Chen,G. F. Ji,L. C. Cai,&Z. W. Gu.(2014).Ab initio studies on phase transition, thermoelastic, superconducting and thermodynamic properties of the compressed cubic phase of AlH3.Journal of Applied Physics,115(12).
MLA Y. K. Wei,et al."Ab initio studies on phase transition, thermoelastic, superconducting and thermodynamic properties of the compressed cubic phase of AlH3".Journal of Applied Physics 115.12(2014).
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