EXAFS parameters and VDOS in zincblende structures

The local dynamical behaviour of the tetrahedrally coordinated semiconductors Ge, CdTe and CuCl, affected by negative thermal expansion at low temperatures, has been recently investigated by EXAFS. Parallel and perpendicular first-shell mean square relative displacements (MSRDs) are here discussed in terms of correlation and anisotropy. The Einstein frequencies are compared with the vibrational densities of states (VDOS). For all considered systems, the perpendicular Einstein frequency is situated between the VDOS structures due to transverse and longitudinal acoustic modes, while the parallel frequency is situated between the VDOS structures due to longitudinal acoustic and optic modes.