Phonon-electron interaction and vibration correlations in germanium within a broad temperature interval

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The temperature dependence of the ``forbidden'' reflection 006 in a germanium single crystal was studied from 299 to 735 K using x-ray resonant scattering at the K-absorption edge. Since the intensity is found to increase by a factor of almost 8 for the maximum temperature, the reflection intensity is dominated by phonon-electron interactions. A theory is developed, which relates the ``forbidden'' reflection intensity to the vibration correlations, u_² and u_⊥², of neighboring atoms, and it is inferred that u_² provides the main contribution to the thermal-motion-induced anisotropy of x-ray resonant scattering.