FIRST-PRINCIPLES INVESTIGATION OF SnO₂ AT HIGH PRESSURE

Abstract

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 [Formula: see text] 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.

Ab initioand shell model studies of structural, thermoelastic and vibrational properties of SnO2under pressure

“…The transition to the CaCl 2 -type structure with pressure corresponds to a small rotation of these octahedra around the tetragonal axis and the deformation to an orthorhombic cell occurring in a continuous way, which indicates a second-order transition [3]. This transition has been studied by several experimental [4][5][6] and theoretical methods [7][8][9]. It has been also found and extensively analyzed for other isomorphous compounds [10][11][12][13][14][15].…”

“…Theoretical ab initio calculations at the B3LYP level [7] have predicted P c ≈ 12 GPa. A study using the linearized augmented plane-wave method (LAPW) [8] leads to P c = 12.4 GPa (GGA) and 10.1 GPa (LDA).…”

Ab Initio Studies of Structure, Electronic Properties, and Relative Stability of SnO2 Nanoparticles as a Function of Stoichiometry, Temperature, and Oxygen Partial Pressure

“…Lattice constants a and c are in units of Å, V 0 is in units of Å 3 and bulk modulus B 0 in GPa. u is a dimensionless parameter. b Ref . c Ref . d Ref . e Ref . f Ref . g Ref . …”

“…Pseudopotentials for atoms in the compound and extensive testings to reproduce SnO 2 crystal properties were generated and reveal that the inclusion of 4d electrons in the Sn core results in an improvement in equilibrium volume, electronic structures, and phonon properties, compared with when they are included in the valence set. 22,23,34,35 The search for the optimized simple basis transferable to nanoparticles should reproduce not only structural properties but also elastic properties and the phonon dispersion curve found in the bulk. The new base results, simple zeta, obtained with a pseudopotential with the same cutoff radius but with a slightly excited configuration for the Sn atom closest to the s 1 p 3 hybrid covalent bond, allow a good convergence of static and dynamic parameters with a lower cutoff energy (175 Ry) and provide similar results (lattice parameters and phonon frequencies) to those obtained with a more complete base as previously described and applied to the bulk.…”

“…The basis set is constructed using Sankey-Niklewski type pseudoatomic orbitals (PAO) generalized to include single and double-ζ decay and are used to represent valence wave functions. Pseudopotentials for atoms in the compound and extensive testings to reproduce SnO 2 crystal properties were generated and reveal that the inclusion of 4d electrons in the Sn core results in an improvement in equilibrium volume, electronic structures, and phonon properties, compared with when they are included in the valence set. ,,, …”