Vibrational Modes in ZnSi${\mathrm{P}}_2$

The optical-phonon spectrum of ZnSi${\mathrm{P}}_2$ has been investigated by polarized Raman scattering at 6328 Å. The results are compared with phonon modes in related tetrahedrally coordinated compounds and with a set of symmetry coordinates. The low-frequency dielectric constants are estimated from the Lyddane-Sachs-Teller (LST) relation and measured refractive indices. Exciton-phonon coupling in ZnSi${\mathrm{P}}_2$ is discussed briefly in connection with recent luminescence measurements.