Ab initio calculations of elastic constants and thermodynamic properties of Li2O for high temperatures and pressures

The elastic constants and thermodynamic properties of Li2O for high temperatures and pressures are calculated by the ab initio unrestricted Hartree–Fock (HF) linear combination of atomic orbital (LCAO) periodic approach. The lattice constant, elastic constants, Debye temperature, and thermal expansion coefficient obtained are in good agreement with the available experimental data and other theoretical results. It is found that at zero pressure the elastic constants C 11 , C 12 and C 44 , bulk modulus B and Debye temperature Θ D decrease monotonically over the wide range of temperatures from 0 to 1100 K. When the temperature T > 1100 K , C 12 approaches zero, consistently with the transition temperature 1200 K. However, with increasing pressure, they all increase monotonically and the anisotropy will weaken.