Temperature dependence of optical activity and circular dichroism in α‐ZnP2 crystals

The circular birefringence related to the gyration components along and perpendicular to the optical axis and the circular dichroism of tetragonal α-ZnP 2 single crystals are determined in the temperature range 290-450K, using universal null-polarimetric techniques. The oscillatory temperature behaviour of the optical rotatory power and the ellipticity of light passed through the crystal in the (001) direction is quantitatively well explained by the influence of multiple reflections of light. The observed thermal hysteresis and dependence of the gyration on sample prehistory testify indirectly the availability of incommensurately modulated structure in α-ZnP 2 .