Structural, elastic and lattice dynamical properties of the alkali metal tellurides: First-principles study

We report a detailed first-principles density functional calculations to understand the systematic trends for crystal structure, elastic and lattice dynamical properties of the anti-fluorite alkali metal tellurides M2Te depending from the type of the M cations (M are Li, Na, K and Rb). The calculated equilibrium lattice parameters are in very good agreement with the available experimental data. Single-crystal and polycrystalline elastic moduli and their related properties of the title compounds were calculated via the stress-strain method. The relatively weak values of the calculated elastic moduli demonstrate the weak resistance of these compounds to applied external forces. Phonon dispersion curves throughout the Brillouin zone and corresponding density of states were calculated using the linear response approach. No imaginary phonon modes were found, which indicate the dynamical stability of the examined materials. The atomic displacements at Gamma point were determined. Low-frequency dielectric properties and infrared response were investigated.