An improved interatomic potential for Ge

Two classes of interatomic potentials for germanium are presently available: (i) a Stillinger-Weber-type potential with different parametrizations, and (ii) a Tersoff-type potential. The evaluation shows that one group of potentials overestimates the melting temperature considerably, whereas the other group does not give the correct values for the lattice parameter and the cohesive energy. In the present work an improved Stillinger-Weber-type potential is developed by adjusting the two three-body parameters in such a manner, that the potential yields the correct lattice constant and the correct cohesive energy, and the melting point and other properties are reproduced satisfactorily. The influence of the three-body parameters on the structural and thermal properties is investigated in detail. Besides the lattice constant, the cohesive energy, and the melting point, the elastic constants and the thermal expansion coefficient of the diamond structure are considered. Furthermore, the properties of the liquid and the amorphous state as well as different crystalline structures of Ge are studied. Particular attention is paid to point defects and self-diffusion in the diamond structure. The influence of the three-body parameters on the formation and migration energies of vacancies and self-interstitials is investigated.