TEMPERATURE-DEPENDENCE OF CORE AND VALENCE THERMAL VIBRATIONS IN GERMANIUM

An X-ray analysis is made for the core and valence thermal vibrations in germanium, using powder X-ray intensity data collected at various t emperatures (298, 573, and 733 K). The overall thermal vibration is sp lit into the components of core and valence thermal vibrations, becaus e the valence electrons oscillate with different phase and amplitude t han the core electrons due to bond polarizability. The data collected at the above temperatures are analyzed using locally developed compute r programs. In the first phase, the overall Debye-Waller factors are e stimated. Then in the second phase, the core and valence contributions of the thermal vibrations are refined. The error in the fitting proce dure is found to be less than 2%, and in the third phase an attempt is made to refine the individual anharmonic thermal parameters (beta(cor e) and beta(val)), which result in unrealistic thermal parameter value s. Hence only the overall anharmonic thermal parameters are evaluated and the results are reported.