Ab initio study of the enthalpy barriers of the high-pressure phase transition from the cubic-diamond to the β-tin structure of silicon and germanium

The elemental semiconductors silicon and germanium have a phase diagram characterized by various high-pressure phases. In recent years, interest has grown on the complex mechanism of the phase transitions in these materials. Here, we present a theoretical investigation of the phase transition from the cubic diamond to the β-tin structure of Si and Ge. This work has been performed using the plane-wave pseudopotential approach to density-functional formalism within the local-density approximation. We have calculated the energy surface as a function of the two relevant lattice parameters. From this surface we obtained the enthalpy barrier which must be crossed during the phase transition. Our data are compared with results of other theoretical and experimental works: An excellent agreement of both the equilibrium parameters and critical values with experimental data is obtained. Finally, we discuss the influence of corrections related to the finite number of plane waves used in the calculation.