First principles studies of SnO at different structures (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.
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.
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.
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
Computational Materials Science, 2012
We have carried out a first-principles density functional study of the structural, elastic and thermodynamic properties for the SnMg 2 O 4 , SnZn 2 O 4 and SnCd 2 O 4 cubic normal spinel structures. We have calculated the equilibrium structural parameters: the lattice constant and internal structural parameter. These results agree very well with experimental data. We have investigated the zero-pressure single-crystal and polycrystalline elastic constants and their related properties, confirming prior theoretical results for SnMg 2 O 4 and predicting values for SnZn 2 O 4 and SnCd 2 O 4. The pressure dependence of the elastic constants C ij can be fit by a straight line over the range 0-30 GPa. Thermal and pressure effects on some macroscopic properties of SnMg 2 O 4 , SnZn 2 O 4 and SnCd 2 O 4 are predicted using the quasi-harmonic Debye model in which the lattice vibrations are taken into account.
First-principles study of SnO under high pressure
This article reports the first-principles study of SnO under high pressure within the generalized gradient approximation (GGA). We have calculated the structural, elastic, electronic and optical properties of SnO. The elastic properties such as the elastic constants Cij, bulk modulus, shear modulus, Young modulus, anisotropic factor, Pugh ratio, Poisson's ratio are calculated and analyzed. Mechanical stability of SnO at all pressure is confirmed using Born stability conditions in terms of Cij. It is also found that SnO exhibits very high anisotropy. The energy band structure and density of states are also calculated and analyzed. The results show the semiconducting and metallic properties at 0 (zero) and high pressure, respectively. Furthermore, the optical properties are also calculated. All the results are compared with those of the SnO where available but most of the results at high pressure are not compared due to unavailability of the results.
Electronic and structural properties of SnO under pressure
Physical Review B, 2005
Pressure-induced changes in the electronic and structural properties of tin monoxide are examined by means of ab initio density-functional calculations. Also, the pressure shifts of the A 1g and E g zone-center phonon modes are derived. The results are compared to recent experimental high-pressure data as well as to previous calculations for ambient conditions. In agreement with earlier findings we observe that the Sn-5s lone pair is not inert but hybridizes with the O-p states. Differences in that respect between SnO and PbO are shown to be a "relativistic dehybridization effect" caused by the large mass-velocity downshift of the Pb-6s states. SnO is a small-gap ͑indirect͒ semiconductor at ambient pressure, but an insulator-metal transition occurs as pressure is applied. The transition is estimated to occur around 5 GPa. The gap depends sensitively on the distance between the layers dE gap / d ln͑c / a͒Ϸ21 eV.
Superlattices and Microstructures, 2015
In this paper we have investigated the structural, electronic and thermodynamic properties of tin oxide (SnO 2) using the full-potential linearized augmented plane wave method (FP-LAPW) within the framework of density functional theory (DFT) as implemented in the Wien2k package within the generalized gradient approximation (GGA) and GGA plus trans-blaha-modified Becke-Johnson (TB-mBJ) as the exchange correlation. From the electronic properties, SnO 2 has a direct band gap in (Γ-Γ) direction with a value of 2.86 eV. The quasi-harmonic Debye model, using a set of total energy versus volume calculations is applied to study the thermal and vibrational effects. Temperature and pressure effects on the structural parameters, such as thermal expansion, heat capacities and Debye temperature are investigated from the non-equilibrium Gibbs function.
Computational study of rutile tin-oxide ( SnO 2 )
2011
Rutile structured tin-oxide ceramics have been intensively studied in recent years because of their potential in sensing and fuel cells. The present work uses classical molecular dynamics simulations focused on the structure and possible transformation of rutile tin-oxide to other phases. The empirical Buckingham potential has been used to describe the interatomic interactions in tin-oxide. The total energy of the NPT hoover ensemble at various temperatures has been calculated in order to determine the transition temperature and pressure. The results obtained showed an energy increase with temperature which was constantly compared with experiments. The radial distribution functions for the two structures suggest the transformations at temperature above 900 K in agreement with the experiments.
Structural and electronic properties of SnO2
Journal of Alloys and Compounds, 2013
Highly transparent polycrystalline thin film of SnO 2 (tin dioxide) was deposited using a simple and low cost spray pyrolysis method. The film was prepared from an aqueous solution of tin tetrachloride (stannic chloride) onto glass substrates at 400°C. A range of diagnostic techniques including X-ray diffraction (XRD), UV-visible absorption, atomic force microscopy (AFM), scanning electron microscopy (SEM), and synchrotron-based X-ray photoelectron spectroscopy (XPS) were used to investigate structural, optical, and electronic properties of the resulting film. Deposited film was found to be polycrystalline. A mixture of SnO and SnO 2 phases was observed. The average crystallite size of $21.3 nm for SnO 2 was calculated by Rietveld method using XRD data. The oxidation states of the SnO 2 thin film were confirmed by the shape analysis of corresponding XPS O 1s, Sn 3d, and Sn 4d peaks using the decomposition procedure. The analysis of the XPS core level peaks showed that the chemical component is non-stoichiometric and the ratio of oxygen to tin (O/Sn) is 1.85 which is slightly under stoichiometry.