Open AccessA SUPERCELL LDA-LMTO-ASA CALCULATION OF COMPOSI-TION DEPENDENCE OF HOPFIELD CONSTANT AND Tc IN Ba1-xKxBiO3
Author(s) -
Yuemao Shen,
Huang Mei-Chun
Publication year - 1992
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.41.1517
Subject(s) - supercell , condensed matter physics , coupling constant , superconductivity , debye model , physics , materials science , constant (computer programming) , electronic band structure , quantum mechanics , thunderstorm , meteorology , computer science , programming language
The electronic structure of (Ba1-xKx)BiO3 has been calculated by using a supercell LDA-LMTO-ASA method at some compositions. The calculation was performed by doubling unit-cell for x=0.25, 0.5 and 1.0 and by quadruple unit-cell for x = 0.25 and 0.75. The band parameters, total density of states TDOS (EF), partial DOS PDOS (EF) and self-consistent potential Vt(r), obtained from LMTO calculation were combined with the experimental Debye temperature ΘD From this, the Hopfield constant ηt, electron-phonon coupling constant λ and superconducting transition temperature Tc and its x-dependence were evaluated by the McMillan theory and Gaspari-Gyorffy approximation. It was found that the λ≈1 and the maximum Tc≈ 10K which is a slowly varying function of composition x. Our results exhibit a significant difference between the traditional theory and experiment and imply a mechanism which would be related to the composition dependent structure transformation besides the BCS methanism.