Elastic and thermodynamic properties of fcc-6Li2O under high temperatures and pressures

Abstract The elastic and thermodynamic properties of fcc - 6 Li 2 O under high temperatures and pressures are investigated using the Density functional theory and quasi-harmonic Debye model. Calculation indicates that the lattice constant of 6 Li 2 O at ground state is a little larger than that of 7 Li 2 O. Pressure can suppress thermal expansion effectively. When it is 1200 K, just only 8.59 GPa can pressure restrain the volume expansion caused by temperature. Elastic constants illuminate that crystal lattice of 6 Li 2 O is mechanical stable under high temperature and temperature. Compared with 7 Li 2 O, shear of 6 Li 2 O on the {1 0 0} and {1 1 0} planes caused by high pressure and temperature is lower. Heat capacity of different pressure increases with temperature and closes to the Dulong–Petit limit at higher temperatures. Debye temperature decreases with temperature, and increases with pressure. Under lower pressure, thermal expansion coefficient raise rapidly with temperature, and then the increasing trend will get slow at higher pressure and temperature.