A phase-difference approach to EXAFS analysis of germanium polymorphs

Two germanium polymorphs of the diamond type and the ST-12 structure were used to investigate the accuracy of extended X-ray absorption fine structure (EXAFS) analysis with a phase-difference method. This method gives similar accuracies to both conventional curve-fitting and Fourier-transform methods in determining the difference of the first- neighbor distances for these two polymorphs. The number of first-shell atoms of the ST-12 structure was determined to be 4.0 ± 0.2 with the diamond-type phase as a standard. In addition, the first-neighbor coordination of amorphous germanium was analyzed with this method. These results suggest that the phase-difference method is useful for structure analysis of materials and that it is especially useful for structure analyses under high pressure.