Anharmonicity of lattice vibrations in zinc by elastic neutron scattering

The form of the effective anharmonic one particle potential up to quartic terms is given and the expression of the temperature factor is derived for atoms occupying the sites of the point-group symmetry 6m2. The theory is applied to the analysis of the elastic thermal-neutron scattering data from a single crystal of Zn measured at 295 K and corrected for extinction and inelastic scattering contamination. The data show significant quartic terms. The values obtained for the anharmonic potential parameters correspond to the mean-square amplitudes <u²_x> = 0.0114 (3) Ų and <u²_z> = 0.0257 (5) Ų of the atomic vibrations in the principal directions. The present results are compared with other recent determinations. The discrepancy of the experimental values with theoretical calculations can be accounted for in full by constant-volume anharmonic effects.