Insight into the structural, electronic and elastic properties of AInQ2 (A: K, Rb and Q: S, Se, Te) layered structures from first-principles calculations

First-principles calculations were performed to explore the structural, elastic and electronic properties of the ternary indium chalcogenides AInQ2 (A: K, Rb and Q: S, Se, Te) in both monoclinic and triclinic phases. This study is carried out by using the first-principles pseudopotential plane-wave (PP-PW) method as implemented in CASTEP code. Both the generalized gradient approximation of Perdew-Burke-Ernzerhof scheme (GGA-PBE) and the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional were used to treat the exchange-correlation interactions. In order to confirm the previous reports and to understand the effect of symmetry in determining the physical properties of these layered materials we have calculated the structural and the electronic properties at the equilibrium lattice constant for both the systems. The single-crystal elastic constants Ci j are calculated using the stress-strain approach. The elastic moduli of the polycrystalline aggregates and their related properties are obtained in the framework of Voigt-Reuss-Hill approximations. Electronic band structure indicates the semiconducting behaviour with a direct band gap at Γ-Γ. The results obtained from the (HSE06) hybrid functional are in excellent agreement with the available experimental data and computed results for the monoclinic and triclinic structures.