0000000000335714
AUTHOR
P. Munsch
Observation of the Cinnabar Phase in ZnSe at High Pressure
In this paper we describe the results of an energy dispersive X-ray diffraction experiment carried out in the ZnSe 1 m x Te x alloy and pure ZnSe under high pressure. In the downstroke the cinnabar phase is observed between the rocksalt and the zincblende phases. The analysis of the whole series of compositions ( x =0, 0.05, 0.1 and 0.2) enables us to establish its lattice parameters in ZnSe ( a =3.785 + and c =8.844 + at 10.5 GPa). The X-ray diffraction pattern simulation suggests that the internal parameters u and v are close to 0.5, indicating that the cinnabar phase in ZnSe is similar to that observed in GaAs and ZnTe. The cinnabar's stability range decreases as the Te content is reduce…
Cinnabar phase in ZnSe at high pressure
We have performed an energy-dispersive x-ray-diffraction experiment on ${\mathrm{ZnSe}}_{1\ensuremath{-}x}{\mathrm{Te}}_{x}$ alloys under high pressure with $x=0,$ 0.05, 0.1, and 0.2. In the downstroke a hexagonal phase appears. We suggest that this phase is cinnabar, whose stability range decreases as the Te content is reduced. The analysis of the whole series of compositions enables us to establish its lattice parameters in ZnSe $(a=3.785\AA{}$ and $c=8.844\AA{}$ at 10.5 GPa). The extinction of some diffraction peaks also suggests that the internal parameters u and $v$ are close to 0.5, indicating that the cinnabar phase in ZnSe is similar to that observed in GaAs and ZnTe.
XRD and XAS structural study of CuAlO2under high pressure
International audience; We present the results of x-ray diffraction and x-ray absorption spectroscopy experiments in CuAlO2 under high pressure. We discuss the polarization dependence of the x-ray absorption near-edge structure at the Cu K-edge. XRD under high pressure evidences anisotropic compression, the a-axis being more compressible than the c-axis. EXAFS yields the copper-oxygen bond length, from which the only internal parameter of the delafossite structure is deduced. The combination of anisotropic compression and the internal parameter decrease results in a regularization of the AlO6 octahedra. The anisotropic compression is related to the chemical trends observed in the lattice pa…
Structural evolution of theCuGaO2delafossite under high pressure
We have performed pseudopotential calculations and x-ray-diffraction and x-ray-absorption measurements on the ${\mathrm{CuGaO}}_{2}$ delafossite under high pressure. We have completely characterized the structural behavior of the low pressure phase. We have found out that the a axis is more compressible than the c axis, and as a consequence the oxygen octahedra defined by the gallium environment tend to become more regular under high pressure. We have determined the internal parameter describing the oxygen position inside the unit cell, and seen that it is nearly constant when pressure is applied. We have observed an irreversible phase transition affecting the copper environment but not the…
GaS and InSe equations of state from single crystal diffraction
We have performed single crystal angle dispersive X-ray diffraction at high pressure in order to investigate the GaS and InSe equations of state. We situate the transition from β-GaS to GaS-II at 2 7 0 3. ± . GPa. In the InSe experiment we locate the beginning of the phase transition at 7.6 ± 0.6 GPa. The equations of state of β-GaS ( 0 43 27 0 06V = . ± . Å 3 , 37 2 GPaB = ± , 5 2B = .¢ ), GaS-II ( 0 42 4 0 2V = . ± . Å 3 , 50 3 GPaB = ± and 4 3 0 3B = . ± .¢ ) and γ-InSe ( 0 58 4 0 2V = . ± . Å 3 , 24 3 GPaB = ± and 8 6 0 8B = . ± .¢ ) are discussed and compared with the results of an ab-initio calculation.
EXAFS Study of PressureInduced Phase Transition in SrWO4
Pressure-induced scheelite-to-wolframite structural phase transition in SrWO4 was studied using two complementary techniques—x-ray absorption spectroscopy and x-ray diffraction (XRD). In situ XRD and W L3-edge EXAFS measurements were performed using the synchrotron radiation. The experiments were done at room temperature in the pressure range from 0 to 30 GPa using the diamond anvil cell. The XRD results unambiguously show that SrWO4 transforms from the tetragonal scheelite phase to the monoclinic wolframite-type phase at about 11.7 GPa. Locally this transition appears as a change of the tungsten ions coordination from regular tetrahedral to distorted octahedral. The analysis of the EXAFS d…