Chemical and Materials Engineering Vol. 5(3), pp. 65 - 74
DOI: 10.13189/cme.2017.050302
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Pressure Induced Structural Phase Transition, Metallization and Superconductivity in KI


Y. Ramola 1, C. Nirmala Louis 1,*, A. Amalraj 2
1 Research Center of Physics, Holy Cross College, Nagercoil, Tamil Nadu, India
2 Associate Professor of Chemistry, St. Jerome's College, Anandhanadarkudy, KK District, Tamil Nadu, India

ABSTRACT

The self-consistent band structure calculation for potassium iodide (KI) performed both in NaCl and CsCl structures using the full potential linear muffin-tin orbital (FP-LMTO) method is reported. The equilibrium lattice constant, bulk modulus and the phase transition pressure at which the compound undergoes structural phase transition from NaCl to CsCl are predicted from the total energy calculations. The band structure, density of states (DOS), electronic charge distributions, metallization and superconducting transition temperature (Tc) of KI are obtained as a function of pressure for both in NaCl and CsCl structures. The density of states at the Fermi level (N(EF)) gets enhanced under pressure, which leads to metallization in KI. It is found that, the charge transfer from s and p states to d state causes structural phase transition and superconductivity in KI. The pressure corresponding to structural phase transition from NaCl structure (B1) to the CsCl structure (B2) is 0.02 Mbar in KI. This value is agreement with the experimental value of 0.019 Mbar. In KI, the metallization occurs through indirect closing of the band gap between Γ and H points at the reduced volume V/Vo=0.43 (CsCl structure), the corresponding metallization pressure is 1.228Mbar. Our results completely agree with the experimental observation of 1.31 Mbar. The highest Tc estimated is 2.151 K and the corresponding pressure is 4.945 Mbar in the NaCl structure and 0.107 K in the CsCl structure.

KEYWORDS
Band Structure, Metallization, Structural Phase Transition, KI, High Pressure Superconductivity

Cite this paper
Y. Ramola , C. Nirmala Louis , A. Amalraj (2017). Pressure Induced Structural Phase Transition, Metallization and Superconductivity in KI. Chemical and Materials Engineering, 5 , 65 - 74. doi: 10.13189/cme.2017.050302.