Dr. C NirmalaLouis, Y Ramola, Dr. A Amal Raj
We have investigated the pressure dependent band structure, density of states, metallization, structural phase transition and superconductivity of cubic rocksalt (NaCl structure) type LiBr using FP-LMTO method. LiBr becomes metal and then superconductors under high pressure, but before that they undergo structural phase transition from NaCl to CsCl structure. The ground state properties and band gap values are compared with the experimental and previous theoretical results. When the pressure is increased there is enhanced overlapping between the wave functions of the neighbouring atoms. As a result the widths of the valence and empty conduction bands increase. These changes lead to the narrowing and closing of band gaps in LiBr (metallization). The mechanism for the phase transition is a geometric effect involving a change in the coordination number from 6 in the NaCl phase to 8 in the CsCl phase. The calculated Tc values depend more sensitively on changes in l than m*, indicating that LiBr is electron-phonon-mediated superconductors. It is also confirmed that structural phase transition, metallization and superconductivity do not occur simultaneously in LiBr.
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