Two Dense Semiconducting Phases of Liinte2 Under High Pressure

Abstract

Ternary semiconducting chalcogenides have been receiving much attention in recent years and appear to be promising candidates for technological applications including solar cells and nonlinear optics. Two novel dense phases with hexagonal P63mc and trigonal [[EQUATION]] space symmetries were firstly identified for the typical Li-based ternary chalcogenide LiInTe2 under high pressure, using the advanced particle swarm methodology for crystal structure search. Pressure-induced structure transition of LiInTe2 from ambient-pressure chalcopyrite [[EQUATION]] to the hexagonal P63mc structure was determined above 0.9 GPa, while a competitively metastable [[EQUATION]] structure was also discovered. The [[EQUATION]] → P63mc phase transition was characterized as first-order with a large volume drop of 19.1%. In contrast to [[EQUATION]] phase with a direct band gap, both P63mc and [[EQUATION]] phases display a much narrower indirect band gap of 0.376 eV and 0.531 eV, stemming from the increase coordination number of Li/In from 4 to 6 and the resulting modification of atomic chemical bonding. Strong ionic bonding feature in these two high-pressure structures was further revealed through a topological analysis of charge density. Finally, compared to ambient[[EQUATION]] phase, their more excellent optical absorption efficiencies in the visible photon energy range were demonstrated by the calculated fundamental optical parameters.

Keywords: LiInTe2 chalcogenide, crystal structure prediction, pressure-induced phase transition, Electronic structure, optical properties