Phonon Anomalies in Transition-Metal Carbides

Abstract

The phonon anomalies observed in superconducting TaC have been explained recently by Weber, Bilz, and Schröder with their extended shell model. Their model also predicts an anomaly in the transverse acoustic mode in the [110] direction with $\mathrm{xy}$ polarization—a branch which was not measured in the initial neutron investigation. The purpose of this Letter is to report the experimental confirmation of the Weber-Bilz-Schröder prediction, which gives added credence to their model, and to comment on the possible significance of these results.