Structural and elastic properties of defect chalcopyrite HgGa2S4 under high pressure (original) (raw)
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High-pressure study of the structural and elastic properties of defect-chalcopyrite HgGa2Se4
Journal of Applied Physics, 2013
In this work, we focus on the study of the structural and elastic properties of mercury digallium selenide (HgGa 2 Se 4 ) which belongs to the family of AB 2 X 4 ordered-vacancy compounds with tetragonal defect chalcopyrite structure. We have carried out high-pressure x-ray diffraction measurements up to 13.2 GPa. Our measurements have been complemented and compared with total-energy ab initio calculations. The equation of state and the axial compressibilities for the lowpressure phase of HgGa 2 Se 4 have been experimentally and theoretically determined and compared to other related ordered-vacancy compounds. The theoretical cation-anion and vacancy-anion distances in HgGa 2 Se 4 have been determined. The internal distance compressibility in HgGa 2 Se 4 has been compared with those that occur in binary HgSe and eÀGaSe compounds. It has been found that the Hg-Se and Ga-Se bonds behave in a similar way in the three compounds. It has also been found that bulk compressibility of the compounds decreases following the sequence "e-GaSe > HgGa 2 Se 4 > HgSe." Finally, we have studied the pressure dependence of the theoretical elastic constants and elastic moduli of HgGa 2 Se 4 . Our calculations report that the low-pressure phase of HgGa 2 Se 4 becomes mechanically unstable above 13.3 GPa. V C 2013 American Institute of Physics.[http://dx.
Crystal structure of HgGa2Se4 under compression
Materials Research Bulletin, 2013
We report on high-pressure x-ray diffraction measurements up to 17.2 GPa in mercury digallium selenide (HgGa 2 Se 4). The equation of state and the axial compressibilities for the low-pressure tetragonal phase have been determined and compared to related compounds. HgGa 2 Se 4 exhibits a phase transition on upstroke towards a disordered rock-salt structure beyond 17 GPa, while on downstroke it undergoes a phase transition below 2.1 GPa to a phase that could be assigned to a metastable zinc-blende structure with a total cation-vacancy disorder. Thermal annealing at low-and high-pressure shows that kinetics plays an important role on pressure-driven transitions.
Vibrational study of HgGa2S4 under high pressure
Journal of Applied Physics, 2013
Stimulated crystallization of melt-quenched Ge2Sb2Te5 films employing femtosecond laser double pulses J. Appl. Phys. 112, 123520 (2012) Controlled joining of Ag nanoparticles with femtosecond laser radiation J. Appl. Phys. 112, 123519 (2012) Structural, elastic, and vibrational properties of layered titanium dichalcogenides: A van der Waals density functional study
First-principles study of structural, elastic and high-pressure properties of cerium chalcogenides
Physica B: Condensed Matter, 2005
First-principles calculations of the structural, elastic and lattice dynamical properties of chalcopyrite BeSiV 2 and MgSiV 2 (V = P, As, Sb) have been performed within density functional theory using normconserving pseudopotentials and generalized-gradient approximation. The obtained equilibrium structural parameters are in good agreement with available experimental and theoretical results. Single-crystal elastic constants, linear and volume compressibilities, shear anisotropic factors, as well as polycrystalline bulk, shear and Young's modulus and Poisson's ratio have been predicted. Our results show that, compared with BeSiV 2 , more pronounced tetragonal distortion and larger elastic anisotropy in both compression and shear have been found in MgSiV 2 compounds. Chalcopyrite BeSiV 2 and MgSiV 2 have been classified as brittle and ductile materials, respectively. Phonon dispersion relations, phonon density of states, infrared absorption spectra and Raman scattering spectra have been calculated using the linear response method. Besides, the phonon frequencies and atomic displacement patterns for Raman-active (E, B 2 , B 1 and A 1 ), infrared-active (E and B 2 ), and silent (A 2 ) modes at zone-center C point have been analyzed in detail. The character of vibrational spectra have been found to be governed by both chemical bonding strengths and masses of structural units. Moreover, the Si-V bonding is remarkably stronger than the Mg-V bonding in MgSiV 2 chalcopyrite semiconductors.
Pressure-induced band anticrossing in two adamantine ordered-vacancy compounds: CdGa2S4 and HgGa2S4
Journal of Alloys and Compounds, 2021
This paper reports a joint experimental and theoretical study of the electronic band structure of two ordered-vacancy compounds with defect-chalcopyrite structure: CdGa 2 S 4 and HgGa 2 S 4. High-pressure optical-absorption experiments (up to around 17 GPa) combined with first-principles electronic bandstructure calculations provide compelling evidence of strong nonlinear pressure dependence of the bandgap in both compounds. The nonlinear pressure dependence is well accounted for by the band anticrossing model that was previously established mostly for selenides with defect chalcopyrite structure. Therefore, our results on two sulfides with defect chalcopyrite structure under compression provide definitive evidence that the nonlinear pressure dependence of the direct bandgap is a common feature of adamantine ordered-vacancy compounds and does not depend on the type of anion.
Physica B: Condensed Matter, 2006
The full-potential linearized augmented plane wave method (FP-LAPW) within the generalized gradient approximation (GGA) is used to calculate the electronic band structures and the total energies of BaS, CaSe and CaTe in NaCl and CsCl-type structures. The latter provide us with the ground states properties such as lattice parameter, bulk modulus and its pressure derivative, elastic constants and the structural phase stability of these compounds. The transition pressures at which these compounds undergo the structural phase transition from NaCl to CsCl phase are calculated. The energy band gaps and their volume dependence in NaCl and CsCl type-structures are investigated. The pressure and the volume at which band overlap metallization occurs are also determined. The ground state properties, the transition and metallization pressures (volumes) are found to agree with the experimental and other theoretical results. The elastic constants at equilibrium in both NaCl and CsCl structures are calculated and compared with the available theoretical results for CaSe, while for BaS and CaTe the elastic constants are not available.
Vibrational properties of CdGa2S4 at high pressure
Journal of Applied Physics, 2019
Raman scattering measurements have been performed in cadmium digallium sulphide (CdGa2S4) with defect chalcopyrite structure up to 25 GPa in order to study its pressureinduced phase transitions. These measurements have been complemented and compared with lattice-dynamics ab initio calculations including the TO-LO splitting at high pressures in order to provide a better assignment of experimental Raman modes. In addition, experimental and theoretical Grüneisen parameters have been reported in order to calculate the molar heat capacity and thermal expansion coefficient of CdGa2S4. Our measurements provide evidence that CdGa2S4 undergoes an irreversible phase transition above 15 GPa to a Raman-inactive phase, likely with disordered rocksalt structure. Moreover, the Raman spectrum observed on downstroke from 25 GPa to 2 GPa has been attributed to a new phase, tentatively identified as a disordered zincblende structure, that undergoes a reversible phase transition to the Raman-inactive phase above 10 GPa.
High-pressure x-ray diffraction studies on HgTe and HgS to 20 GPa
Physical Review B, 1983
HgTe and HgS have been investigated with the use of the high-pressure x-ray diffraction technique to 20 GPa. HgTe undergoes three pressure-induced phase transitions in the (0-20)-GPa range, from zinc blende to cinnabar to rocksalt to P-Sn, at 1.4, g, and 12 GPa, respectively. HgS does not show any evidence for a transition from the cinnabar structure up to 20 GPa, either in high-pressure x-ray diffraction or in high-pressure Raman studies. The above transition sequence agrees with the pressure-induced sequence for CdTe except for the intrusion of the cinnabar structure. Evaluation of the bulk modulus Bo and Bo from high-pressure x-ray data reveals that the cinnabar phases of HgTe and HgS are very compressible; Bo and Bo are 19.4+0.5 GPa and 11.1 for HgS, and 16.0+0.5 GPa and 7.3 for HgTe. Bulk moduli, volume changes for transitions, and lattice parameters of the high-pressure phases have all been determined from the x-ray data. The observed transition sequence for Hg Te appears to be in agreement with the predictions of recent pseudopotential total-energy calculations for phase stability in III-V and II-VI compounds under pressure.
Thermo-elastic and structural properties of thorium chalcogenides: A high pressure study
Solid State Sciences, 2010
The pressure induced phase transition and thermo-elastic properties of Th-chalcogenides have been investigated by means of two different models (i) modified charge-transfer potential model which consists of Coulomb and Coulomb screening due to delocalization of f-electron of the rare-earth atom and modified by covalency and zero-point energy effects and repulsive interactions, and (ii) chargetransfer model which excludes covalency and zero-point energy effects in the previous model. These materials lie in Fm3m phase at ambient conditions and transform to Pm3m phase under pressure due to first-order phase transition (P T ¼ 24.75 and 14.34 GPa) and their equation of state show volume collapse of 8.92 and 9.13%, respectively for ThS and ThSe while ThTe retains Pm3m phase up to 50 GPa. Our results are in good agreement with the experimental data. The elastic and thermal properties of these compounds have also been computed at normal and high pressures. Both the models are capable of explaining the Cauchy's discrepancy, elastic, phase transition and thermophysical properties successfully.
Compressibility of β-As4S4: an in situ high-pressure single-crystal X-ray study
Ambient temperature X-ray diffraction data were collected at different pressures from two crystals of b-As 4 S 4 , which were made by heating realgar under vacuum at 295ºC for 24 h. These data were used to calculate the unit-cell parameters at pressures up to 6.86 GPa. Above 2.86 GPa, it was only possible to make an approximate measurement of the unit-cell parameters. As expected for a crystal structure that contains molecular units held together by weak van der Waals interactions, b-As 4 S 4 has an exceptionally high compressibility. The compressibility data were fitted to a third-order BirchÀMurnaghan equation of state with a resulting volume V 0 = 808.2(2) Å 3 , bulk modulus K 0 = 10.9(2) GPa and K' = 8.9(3). These values are extremely close to those reported for the lowtemperature polymorph of As 4 S 4 , realgar, which contains the same As 4 S 4 cage-molecule. Structural analysis showed that the unit-cell contraction is due mainly to the reduction in intermolecular distances, which causes a substantial reduction in the unit-cell volume (~21% at 6.86 GPa). The cagelike As 4 S 4 molecules are only slightly affected. No phase transitions occur in the pressure range investigated.