Crystal structure of HgGa2Se4 under compression

Abstract

31We report on high-pressure x-ray diffraction measurements up to 17.

X-ray diffraction study on pressure-induced phase transformations and the equation of state of ZnGa2Te4

“…At 12.5 GPa, the new peaks fully develop and the peaks of the low-pressure phase cannot be detected anymore. As found in ZnGa 2 Se 4 and related compounds, [8][9][10][11][12][13] we found that the XRD patterns of the HP structure of ZnGa 2 Te 4 can be assigned to a cubic rocksalt-type structure ðFm 3mÞ, where the Te atoms are located at the 4b site, while the Zn and Ga atoms are located at the 4a sites with a partial SOF. Results of the Rietveld refinements indicating the good match of this disordered rocksalt-type (DR) structure with the experimental results are shown in Fig.…”

“…The irreversibility of the phase transition was already observed in other related AB 2 X 4 compounds 8,10,11,13,25 and it was proposed that the recovered samples transformed to a metastable disordered zincblende-type (DZ) structure ðF 43mÞ at ambient pressure. 8,10,11,13 In our case, we have been able to successfully reproduce the diffraction patterns collected at ambient pressure after decompression by assuming the DZ structure. Residuals and parameters indicating the quality of the structural refinement are given in Fig.…”

“…Details of the structural model are given in Table II. We would like to stress here, that in spite the DR structure was previously assigned to the HP phase of other members of the AB 2 X 4 family, [8][9][10][11][12][13] this is the first time that it is assigned using enough Bragg peaks (fourteen) to be confident on the structural assignment. This was possible thanks to the large unit-cell volume of ZnGa 2 Te 4 and the large angular aperture of the DAC used in the experiments (2h < 25 ).…”

“…Among other techniques, they have been studied by XRD, being several pressure-induced transitions reported. [6][7][8][9][10][11][12][13][14][15] The reversibility of these transitions is subject of dispute. In some cases, it has been found that the transitions are not reversible, being metastable polymorphs recovered at ambient conditions after decompression.…”

High-pressure Raman scattering study of defect chalcopyrite and defect stannite ZnGa2Se4

“…32,33 Therefore, we have tentatively assigned the Raman spectrum at 1.2 GPa in the downstroke to the DZ phase since this structure has been observed on downstroke in several OVCs. [54][55][56][57] We think that the Raman spectrum at 1.2 GPa on downstroke corresponds to the first-order one-phonon density of states of the DZ phase, which shows an average over the phonons of the whole Brioullin zone. The observation of the one-phonon density of states is due to the loss of translational periodicity of the lattice caused by the random distribution of the cations and vacancies at the same Wyckoff site.…”