Abstract
The first-order Raman spectra of trigonal Se and Te have been measured under pressure up to the semiconductor-metal transition points at room temperature. In both materials, a prominent pressure effect is found as an anomalous shift of the A1 mode to low frequency. This softening indicates interference of the interchain bonding with the intrachain covalent bond. Frequency shifts with pressure show deviations from the lattice dynamical homology of Se and Te. The results are interpreted as aspects of the transition to the puckered layer structure of the high-pressure monoclinic phase of Te.
