Local dynamical properties of crystalline germanium and their effects in extended x-ray absorption fine structure

The local dynamics of crystalline germanium has been investigated by molecular-dynamics simulations. The radial distribution functions of the first six coordination shells, as well as their parallel and perpendicular mean-square relative displacements, have been determined as a function of temperature. The agreement with the available extended x-ray absorption fine-structure data is very good. Original insights on the outer shells have been achieved. In particular, differently from the first shell, the bond thermal expansion of the outer shells is mainly due to the shift of the maximum of the distance distribution while the contribution of the distribution asymmetry is smaller than 15%.