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Phonon anomaly in high-pressure Zn

The equation of states and phonon dispersions of hexagonal zinc have been calculated by the plane-wave pseudopotential method within the generalized-gradient approximation. Weak discontinuities are found in the pressure-volume relation as well as the c/a-volume curve. Phonon dispersions of Zn under pressure have been obtained with a direct method and the results are consistent with the neutron scattering data. At V/V0 approximately 0.88, the calculated frequencies of the acoustic phonons near the zone center softened substantially as a result of an electronic topological transition. The theoretical result is consistent with the observed anomaly in the Lam-Mossbauer factor at low temperature.