ANHARMONIC EFFECTS IN GERMANIUM

A precise X-ray investigation is carried out to probe the lowest-order anharmonic contribution of the atomic potential of the germanium atom . A total number of 1052 reflections (h + k + l = 4n and 4n +/- 1) are precisely measured at room temperature using a spherical single cryst al of germanium and using a Nonius CAD-4 X-ray diffractometer with cry stal monochromatized MoKalpha radiation. A least-square refinement pro gram is used to refine the harmonic and anharmonic thermal parameters of the crystal. The refinement gives beta(Ge) = (-0.749 +/- 1.79) x 10 -(16) J nm-3 with B(Ge) = (0.528 +/- 0.004) x 10(-2) nm2. The reliabil ity index (R) amounts to 1.71% for germanium.