Prediction study of the elastic and thermodynamic properties of the SnMg2O4, SnZn2O4 and SnCd2O4 spinel oxides (original) (raw)
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Computational Materials Science, 2011
We investigate the structural, elastic, and electronic properties of rutile-type SnO 2 by plane-wave pseudopotential density functional theory method. The lattice constants, bulk modulus and its pressure derivative are all calculated. These properties at equilibrium phase are well consistent with the available experimental and theoretical data. Especially, we study the pressure dependence of elastic properties such as the elastic constants, elastic anisotropy, aggregate acoustic velocities and elastic Debye temperature H. It is concluded that this structure becomes more ductile with increasing pressure up to 28 GPa. Moreover, our compressional and shear wave velocities V P = 7.02 km/s and V S = 3.84 km/s, as well as elastic Debye temperature H = 563 K at 0 GPa compare favorably with the experimental values. The pressure dependences of band structures, energy gap and density of states are also investigated.
2007
Theoretical investigations concerning the high-pressure polymorphs, the equations of state, and the phase transitions of SnO 2 have been performed using density functional theory at the B3LYP level. Total energy calculations and geometry optimizations have been carried out for all phases involved, and the following sequence of structural transitions from the rutile-type (P4 2 /mnm) driven by pressure has been obtained (the transition pressure is in parentheses): f CaCl 2 -type, Pnnm (12 GPa) f R-PbO 2 -type, Pbcn (17 GPa) f pyrite-type, Pa3 h (17 GPa) f ZrO 2 -type orthorhombic phase I, Pbca (18 GPa) f fluorite-type, Fm3 hm (24 GPa) f cotunnite-type orthorhombic phase II, Pnam (33 GPa). The highest bulk modulus values, calculated by fitting pressure-volume data to the second-order Birch-Murnaghan equation of state, correspond to the cubic pyrite and the fluorite-type phases with values of 293 and 322 GPa, respectively.
First principles studies of SnO at different structures
2010
Purpose: Structural and mechanical properties of the Sn (tin) based oxides SnO and SnO 2 are investigated. The aim of this study to determine in which structural phase SnO is found and to calculate its elastic constants at different pressures.
Journal of Solid State Chemistry
a b s t r a c t The structural, elastic, electronic, and optical properties of cubic spinel MgIn 2 S 4 and CdIn 2 S 4 compounds have been calculated using a full relativistic version of the full-potential linearized-augmented plane wave with the mixed basis FP/APW + lo method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA). Moreover, the Engel–Vosko GGA formalism is also applied to optimize the corresponding potential for band structure calculations. The ground state properties, including the lattice constants, the internal parameter, the bulk modulus, and the pressure derivative of the bulk modulus are in reasonable agreement with the available data. Using the total energy-strain technique, we have determined the full set of first-order elastic constants C ij and their pressure dependence, which have not been calculated or measured yet. The shear modulus, Young's modulus, and Poisson's ratio are calculated for polycrystalli...
Effect of pressure on structural and elastic properties of strontium oxide
NATIONAL CONFERENCE ON PHYSICS AND CHEMISTRY OF MATERIALS: NCPCM2020, 2021
The structural properties strontium oxide (SrO) in two phases, namely, Rocksalt (B1) and Cesium Chloride (B2) phases, and a structural transition from B1 to B2 structures are presented. We have estimated the effect of pressure on structural and elastic properties of SrO semiconducting material using an effective inter-ionic potential method, which contain the long-range Coulomb and van der Waals (vdW) interactions and the short-range repulsive interaction of up to secondneighbor ions within the Hafemeister and Flygare approach. To calculate the vdW coefficients Slater-Kirkwood variational method was used. Our calculated phase transition pressure (Pt) is 38.5 GPa. We have also focused on the elastic properties of SrO compound within the effective inter-ionic potential approach and the second order elastic constants (SOEC) were predicted in both the phases. The present calculations have provided a good agreement with the available data reported on this compound.
Structural phase transition, electronic and elastic properties of rocksalt structure SnAs and SnSb
Pressure induced structural phase transitions in SnAs and SnSb have been studied using ab-initio density functional theory. The phase transition from NaCl to CsCl structure occurs at 29.8 GPa for SnAs, which agrees well with experimental data, while the same for SnSb is found to be 10.6 GPa, reported for the first time. The calculated ground state properties are in good agreement with available experimental and theoretical results. The electronic and bonding properties have also been analyzed. The elastic constants along with other secondary elasticity properties in B 1 (NaCl-type) phase are also estimated at ambient as well as high pressure.
Structural study of SnO at high pressure
Physica B: Condensed Matter, 2006
We have studied the structural behaviour of tin monoxide (SnO) by energy dispersive X-ray diffraction (EDXRD) and EXAFS in a pressure range up to 51 GPa. We found a shear stress induced phase transition to an orthorhombically distorted structure under non hydrostatic conditions. Besides this we observed no phase transition of SnO up to the highest pressure of this study. SnO shows strong anisotropy in compression. The a-axis is rather incompressible with a linear stiffness coefficient of K a0 ¼ 306ð6Þ GPa whereas the stiffness of the c-axis is K c0 ¼ 43ð2Þ GPa. The bulk modulus of SnO is K 0 ¼ 35ð1Þ GPa and its derivative K 0 0 ¼ 6:1ð2Þ. A possible disproportionation of SnO to SnO 2 and Sn at ambient temperature under high pressure is also discussed. r
Elastic constants and their pressure dependences inCd1−xMnxTe with0≤x≤0.52and inCd0.52Zn0.48Te
Physical review, 1985
We have measured ultrasonic transit times to determine the elastic constants of Cdl Mn Te crystals with 0 & x & 0.52 and of Cdo»Zno 4g Te at 296 K using hydrostatic pressures up to 4 kbar. It is found that Mn, but not Zn, weakens the zinc-blende crystal structure and makes it less stable under pressure. Applying a modified Born criterion to our data, we deduce the pressure expected to cause the transition to the rocksalt structure in each compound. The influence of Mn we attribute to Mn 3d orbitals hybridizing into the tetrahedral bonds.
FIRST-PRINCIPLES INVESTIGATION OF SnO 2 AT HIGH PRESSURE
International Journal of Modern Physics B, 2005
The ground state properties and the structural phase transformation of tin dioxide (SnO 2 ) have been investigated using first principle full potential-linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). We used local density approximation (LDA) and the generalized gradient approximation (GGA), which are based on exchange-correlation energy optimization, to optimize the internal parameters by relaxing the atomic positions in the force directions and to calculate the total energy. For band structure calculations, we utilized both the Engel-Vosko's generalized gradient approximation (EVGGA), which optimizes the exchange-correlation potential, and also GGA. From the obtained band structures, the electron (hole) valance and conduction effective masses are deduced. For compressed volumes SnO 2 is shown to undergo two structural phase transitions with increasing pressure from the rutile-to the CaCl 2 -type phase at 12.4 GPa and to a cubic phase, space group pa3 at 22.1 GPa. The calculated total energy allowed us to investigate several structural properties, in particular, the equilibrium lattice constants, bulk modulus, cohesive energy, interatomic distances and the angles between different atomic bonds. In addition, we discuss the bonding parameter in term of charge density, which show the localization of charge around the anion side.
Elastic, optoelectronic, and thermal properties of cubic CSi2N4: an ab initio study
Journal of Materials Science, 2013
The mechanical, optoelectronic, and thermodynamic properties of carbon silicon nitride spinel compound have been investigated using density functional theory. The exchange-correlation potential was treated with the local density approximation (LDA) and the generalized gradient approximation of Perdew-Burke and Ernzerhof (PBE-GGA). In addition, the Engel-Vosko generalized gradient approximation (EV-GGA) and the modified Becke-Johnson potential (TB-mBJ) were also applied to improve the electronic band structure calculations. The ground state properties, including lattice constants and bulk modulus, are in fairly good agreement with the available theoretical data. The elastic constants, Young's modulus, shear modulus, and Poisson's ratio have been determined by using the variation of the total energy with strain. From the elastic parameters, it is inferred that this compound is brittle in nature. The results of the electronic band structure show that CSi 2 N 4 has a direct energy band gap (C-C). The TB-mBJ approximation yields larger fundamental band gaps compared to those of LDA, PBE-GGA, and EV-GGA. In addition, we have calculated the optical properties, namely, the real and the imaginary parts of the dielectric function, refractive index, extinction coefficient, reflectivity, and energy loss function for radiation up to 40.0 eV. Using the quasi-harmonic Debye model which considers the phononic effects, the effect of pressure P and temperature T on the lattice parameter, bulk modulus, thermal expansion coefficient, Debye temperature, and the heat capacity for this compound were investigated for the first time.