Calculation Method of the Lattice Constants of Crystal at Different Temperature and Pressure

Abstract

The lattice constants of crystal are the basis of the valence electron structure calculation with the bond length difference method of the empirical electron theory of the solid and molecules. However, the lattice constants change with temperature and pressure. In this paper, according to the nature of thermal expansion of crystal and generalized Hookes law, the relationships among lattice constants, temperature and pressure are established by using linear thermal expansion coefficient and elastic constant. Taken the lattice constants of hexagonal graphite as an example, the calculation results agree with experimental data greatly, which prove the viability of this calculation method.