MEAN-SQUARE RELATIVE DISPLACEMENTS OF NEAREST-NEIGHBOR ATOMS IN GE

EXAFS spectra of crystalline and amorphous Ge have been used to determine the mean-square relative displacements sigma 2 of nearest- and next-nearest-neighbour atoms in the temperature range 80-400K. A strong correlation of the nearest-neighbour motion is observed for crystalline Ge, but this correlation decreases in the amorphous material. The results are compared with calculations performed within the Debye approximation. The structural parameters of amorphous Ge are consistent with a continuous random network approach.