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

Abstract

The circular birefringence related to the gyration components along and perpendicular to the optical axis and the circular dichroism of tetragonal a-ZnP 2 single crystals are determined in the temperature range 290-450 K, 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 a-ZnP 2 .

Gyration and Permittivity of Ethylenediammonium Sulfate Crystals

“…In the thickness regime of 100 microns or more, the multiple internal reflections inside the slab give rise to several superimposed outgoing waves . For very thick crystals measured at oblique incidence, the multiply reflected waves can be spatially resolved and separately measured, but as the HAUP method relies on transmission measurements at normal incidence, the contribution of multiple reflections is unavoidable, and has lead to artifactual oscillations in recovered values of α as a function of temperature . Moreover, relying on normal incidence requires that crystals be cut in multiple directions, the number of requisite directions being equal to the number of unique components in α .…”

“…What has happened since 2000 in the determination of the chiroptical anisotropy of single crystals? Here is the update: 2000s (18), 2010s (4) . The apparent building of momentum from laboratories around the world has dissipated.…”

On the chiroptical properties of racemic crystals

“…[8][9][10][11] The chances that the data in Gautier et al 1 represent CD or lack thereof are vanishingly small because there is no evidence that the extremely stringent conditions for making such measurements, involving sample preparation, instrument design, and calibration, as well as data reduction and analysis, were satisfied. These spectra are offered as the first measurements of the CD of racemic crystals.…”

“…Credible measurements of the electronic CD along general directions in biaxial crystals in the >200 history of crystal optics can be counted on one hand. [8][9][10][11] The chances that the data in Gautier et al 1 represent CD or lack thereof are vanishingly small because there is no evidence that the extremely stringent conditions for making such measurements, involving sample preparation, instrument design, and calibration, as well as data reduction and analysis, were satisfied. As Michl and Thulstrup remarked, "CD measurements on partially aligned samples are sensitive to experimental artifacts, calling for extreme care in the execution and interpretation of the experiments," one of many warnings in the literature regarding the deleterious consequences of parasitic linear polarizations during attempts to measure chiroptical quantities.…”

Theoretical Study on Electronic, Optical Properties and Hardness of Technetium Phosphides under High Pressure

“…Due to its superior optical properties, CdP 2 has a wide range of application prospects in the fabrication of solar cells [5]. In addition, its large thermo-optic coefficient leads to numerous applications in thermal sensors [6]. Further, its wide band gap and anisotropic electrical properties make CdP 2 a promising material in electronic engineering [7].…”