HgGa₂Se₄ under high pressure: An optical absorption study

Abstract

23High-pressure optical absorption measurements have been performed in defect

Structural and elastic properties of defect chalcopyrite HgGa2S4 under high pressure

“…3shows the experimental (symbols) and theoretical (solid line) pressure dependence of the c/a ratio vs. pressure.It can be observed that c/a increases with increasing pressure from 1.856 at RP to 1.929 at 15.1 GPa. Therefore, our results show that DC-HgGa 2 S 4 , like other DC compounds[18,24,26,27,[31][32][33], tends to a more symmetrical structure on compression.Furthermore, the evolution of the experimental c/a ratio with pressure is also well reproduced by our calculations. It must be noted that the increase of the c/a ratio has been previously considered as a measure of cation-vacancy disorder[60,61].…”

Lattice Dynamics Study of HgGa2Se4 at High Pressures

“…GPa; i.e., close to the transition to the intermediate phase between DC and DR structures. We think that the damage was caused by heating due to the local absorption of the laser energy due to the decrease of the absorption edge energy at the DC to DS phase transition, but also likely due to the presence of some dark linear defects that appear in the sample as onset of the transition to the Raman-inactive phase [69] also noted in previous works in OVCs [28,31,34]. The temperature of the sample induced during laser absorption cannot be measured, but it can be estimated to be only a few hundred degrees since no thermal emission was detected from the sample [70].…”

“…We have shown in a previous study of a thermally-activated cation ordering in ZnGa 2 Se 4 crystal at ambient pressure the small differences in the Raman spectra of the DC phase and one of the polytypes of DS phase[63]. However, in the literature several polytypes of the DS phase with more Raman modes than the original DC phase have been proposed[31,34,44]. Therefore, on the basis of the extra Raman modes observed above 19 GPa and the shift of the modes previously attributed to the DC phase, we tentatively propose that HgGa 2 Se 4 undergoes a DC to DS phase transition above 19GPa.…”

β−Bi2O3under compression: Optical and elastic properties and electron density topology analysis

“…3(b)]. It must be mentioned that despite the fact that this method does not give an accurate value of the bandgap energy, it yields a rather accurate value of the pressure coefficient of the bandgap energy [29]. Figure 4 shows the experimental pressure dependence of the indirect bandgap energy in β-Bi 2 O 3 upon increasing (solid symbols) and decreasing (open symbols) pressure, as obtained from the extrapolation noted in the previous paragraph.…”

“…Afterwards, the experimental transmittance spectrum was scaled to the theoretical transmittance value in the spectral range where the sample is completely transparent. Finally, the absorption coefficient α was obtained from the scaled transmittance by taking into account the sample thickness and reflectivity [29].…”