The a b i n i t i o model potential representation of the crystalline environment. Theoretical study of the local distortion on NaCl:Cu+

Abstract

A b i n i t i o model potential study of local distortions around Cr+ and Cr3+ defects in fluoriteIn this paper we formulate a model potential approach to take into account the crystalline environment within the Hartree-Fock-Roothaan formalism. The formulation is based on the assumption that the theory of separability of many-electron systems may be applicable to the group of electrons within a reference cluster and the groups of electrons on a set of external lattice sites which, in turn, can be represented according to the ab initio model potential method. The characteristics of the model potentials permit to analyze the contributions to the cluster energies and wave functions of different environmental effects, such as point-charge and charge-density Coulomb interactions and quantum interactions (exchange and orthogonality). The formalism is applied to the SCF calculation on the ground state of the octahedaral CuCI~cluster (all-electron calculation) embedded in a NaCllattice which is represented by 118 model-potential ions and 604 point-charge ions. The calculation reveals that (i) the quantum interactions between the CuCI~ -cluster and the rest of the lattice play an important role in determining the Cu-Cl distance and (ii) a considerable local distortion around the Cu + impurity is predicted in which the CI-ions move towards the Cu + impurity about 0.1 A.These results are in qualitative agreement with recent EXAFS studies; however, the predicted distortion is smaller than the one suggested by the EXAFS measurements.

Charge Transfer in Uranyl(VI) Halides [UO2X4]2− (X = F, Cl, Br, and I). A Quantum Chemical Study of the Absorption Spectra

“…In the present study we have chosen to use ab initio model potentials, AIMPs, which describe both classical (electrostatic) and quantum mechanical effects (exchange and linear independence) of the frozen ions on the rest of the system, and normally there are no associated electrons or basis sets. 31,32 These ab initio model potentials are obtained for ions in a crystalline environment. The AIMP method has been successfully used in many applications related to structural and spectroscopic properties of impurities in solids.…”

“…39 For the halide ligands we also used ANO-RCC basis sets of both triple-ζ and quadruple-ζ quality; 39 20 and were obtained in the following crystals: Cs 2 NaYF 6 , 40 Cs 2 NaYCl 6 41 and Cs 2 NaYBr 6 . 41 The embedding potential for iodide ion was produced in this work, following the recipe for the AIMP method 31,32 in the NaI crystal.…”

Embedding Fragment ab Initio Model Potentials in CASSCF/CASPT2 Calculations of Doped Solids: Implementation and Applications

“…The Fragment AIMP method was designed to be a generalization of the AIMP method 5,6 and the same iterative procedure is used to obtain the fragments' orbital energies and coefficients so that (energy-weighted) density matrices are obtained that cluster and fragment orbitals. In order to achieve the AIMP representation, the short range Coulomb and exchange interaction should be represented via non-local operators as it was proposed, for instance, for EFP by von Arnim and Peyerimhoff.…”

Ab initio theoretical study of luminescence properties of Pr3+-doped Lu2O3

“…We have performed spin-free ab initio model potential (AIMP) embedded cluster optimizations of the geometry in relevant electronic states and then, we have calculated vertical transition energies at the optimal geometries. The AIMP embedded cluster method 13,14 has been succesfully applied in a number of structural and spectroscopical studies of lanthanide and actinide-doped ionic hosts. [15][16][17][18][19][20] As a result of the calculations, we obtain the local distortion produced by the Pr 3+ doping and we give support to the assignments of the absorption bands to Pr 3+ occupying different sites in the Lu 2 O 3 lattice 5,6 are supported.…”