A Calculation Approach to Elastic Constants of Crystallinesat High Pressure and Finite Temperature

Elastic constants of Na and Li metals are calculated successfully for temperature up to 350 K and pressure up to 30 GPa using a scheme without involving any adjustable parameter. Elastic constants are assumed to depend only on an effective pair potential that is only determined by the average interatomic distance. Temperature has an effect on elastic constants by way of charging the equilibrium. The elastic constants can be obtained by fitting the relationship between total energy and strain tensor using the new set of lattice parameters obtained by calculating displacement of atoms at the finite temperature and at a fixed pressure. The relationship between effective pair potential and the interatomic distance is fitted by using a series of data of cohesive energy corresponding to lattice parameters.