First-principles study of structural stability, electronic properties and lattice thermal conductivity of KAgX (X = S, Se, Te)

The present study is the first attempt towards establishing computational insights into the structural, electronic, mechanical, dynamical and thermal properties of the tetragonal phases of potassium chalcoargentates (KAgX). We find that the lattice thermal conductivity of KAgX is anisotropic, with values of 0.553 (0.279), 0.509 (0.369) and 0.221 (0.125) Wm(-1)K(-1) at room temperature (300 K) along the a-axis (c-axis) for KAgS, KAgSe and KAgTe, respectively. The calculated values of the lattice thermal conductivity are very small, especially along the c-axis. This highlights the potential of using KAgX in designing thermoelectric materials, since low lattice thermal conductivity is a requisite for maximizing the dimensionless figure of merit which defines the efficiency of a system in converting thermal to electrical energy and vice versa.