Isotopic effects on the lattice constant in compound semiconductors by perturbation theory: An ab initio calculation

The dependence of the crystal lattice constant on isotopic substitution of atomic masses is investigated in GaAs and ZnSe using perturbation theory in a density-functional framework. The temperature dependence of the derivatives of the lattice constant with respect to both the anion and the cation mass is computed. Results for additional lattice properties, such as the linear thermal expansion coefficients and mode Gruneisen parameters, are reported and compared with available experimental data. Chemical trends are discussed.