Lattice Dynamics of YZn

Abstract

Phonon dispersion curves for YZn along the (0, 0, $\zeta$), ($\zeta$, $\zeta$, 0) ($\zeta$, $\zeta$, $\zeta$) and (½, ½, $\zeta$) directions have been measured by inelastic neutron scattering at room temperature. A sixth-neighbor force-constant model was used to obtain a fit to the data; there is residual indication of weak forces of still longer range. The frequency distribution function, Debye temperature as a function of temperature, and mean-square atomic displacements were calculated from the model. No Kohn-type anomaly was observed, and YZn was not found to become superconducting down to 1.2 K. Comparison of the dispersion curves of YZn with those of $\beta$-brass shows some pronounced differences, though there is a coincidence of accidental degeneracy between the transverse acoustical and transverse optical branches in both materials at (0, 0, ½).