Elastic constants and electronic structure of fluorite (CaF₂): an ab initio Hartree-Fock study

Abstract

The ground state properties of fluorite (CaF2) have been studied using CRYSTAL, an ab initio periodic Hartree-Fock program. Twenty-two and thirteen atomic orbitals (repmented as contracted Gaussian-type functions) are used for the calcium and fluorine atoms, respectiwly. The binding energy (BE), the equilibrium lattice parameter (e), theelasticconstants (C,,) and thecmtralzonephononhpquencies ~( I R )and v(Rama0) have been evaluated, and a g d ageenent obtsined with experiment (for instance the error i s t2.0, +1.7, -0.5% for BE, Q and C11, respectively). The calculated Cu elastic constant reduces from 48 to 44 GPa (experimental value: 37 GPa) when the Euorine atoms are allowed to displace under strain. indicating the importance of inner deformation for shear elasticity. Electron density maps, density of states and band struetun plots are reported which confirm the f d y ionic n a t m of fluorite.

Influence of dislocation density on the pop-in behavior and indentation size effect in CaF2 single crystals: Experiments and molecular dynamics simulations

“…A fit of that relation to the universal potential curve delivers a bulk modulus of 81 GPa, comparing well with a median value of 83 GPa found in the literature [33][34][35].…”

Effect of Fock exchange on the electronic structure and magnetic coupling in NiO

“…The cell parameters have been determined for the ferroand antiferromagnetic phases and the elastic constants calculated numerically by fitting the energy with respect to the deformation of the cell following the procedure described by Dovesi et al 71,72 The magnetic form factors have been calculated as the Fourier transform of the ground-state antiferomagnetic spin density.…”

“…Several strategies have been proposed to perform simple cell deformations that permit the calculation of the elastic constants conserving the maximum number of symmetry operators. 48,71,72 Following the deformation of the unit cell, internal relaxation of the atoms may be necessary depending on the space-group symmetry. However, for the present case there are no internal parameters to optimize: all are fixed by symmetry.…”

Ab initio calculations of the atomic and electronic structure of MgF2 (011) and (111) surfaces

“…To achieve high accuracy, large tolerances of 7 8 7 7, and 14 were chosen in calculations of the Coulomb overlap, Coulomb penetration, exchange overlap, first exchange pseudo-overlap, and second exchange pseudo-overlap integrals, respectively 1 . We used the basis sets for F [13] and Mg atoms [14].…”