A. N. Kislov

Study of the electro-absorption spectrum of a nickel acceptor exciton in a ZnO:Ni crystal based on a calculation of vibrations associated with a Ni+1 impurity

Localized vibrations in ZnO crystals due to the substitution impurity Ni+1 are modeled. The calculations were performed in the shell model using a recursive method for vibrations with A1 and E type symmetry. Numerical calculations allowed us to analyze the vibronic structure in the electro-absorption spectra for nickel acceptor excitons in ZnO:Ni.

A vibronic-structure analysis of optical spectra in ZnO:Ni3+ crystals by localized-vibration simulation

A theoretical study is reported of the vibrations associated with a Ni3+ impurity charged with respect to the ZnO lattice. The calculations were made by a recursive method in terms of the shell model for vibrations with different symmetries. The vibronic structure observed in the spectra of d-d intracenter transitions in the Ni3+ impurity has been interpreted using model calculations.

Anharmonicity of lattice vibrations induced by charged nickel impurities in II–VI semiconductors

The lattice vibrations induced by nickel impurities with a negative charge relative to the lattice in ZnSe: Ni, ZnO: Ni, ZnS: Ni, and CdS: Ni semiconductors are investigated using very sensitive field-induced vibronic spectroscopy. This technique is based on the interaction of lattice vibrations with impurity excitons and the effect of an ac electric field on these excitons. The phonon replicas of the zero-phonon line (ZPL) of impurity excitons (including intense peaks of combination replicas up to the eighth order) in the experimental spectra of the system under investigation are observed for the first time. These spectra make it possible to analyze the interaction between different vibrations. The experimental results are interpreted in terms of model calculations of the vibrations in a lattice with a charged impurity center and vibrations in a monoatomic chain with a strong anharmonicity. It is demonstrated that charged impurity centers initiate new lattice vibrations, namely, extrinsic anharmonic modes with a considerable third-or fourth-order anharmonicity.

Interaction of nickel donor and acceptor excitons with defect vibrations in ZnSe:Ni crystals

Defect vibrations in ZnSe:Ni crystals induced by the Ni impurity with charge of ±1 relative to the neutral state are calculated by a recursive method in the shell model. This leads to an interpretation of vibronic structures in electroabsorption spectra for donor and acceptor Ni excitons in ZnSe:Ni crystals.

Model of the lattice dynamics and study of the vibronic structure of intracenter transitions in ZnO:Ni+2 crystals

This paper presents a calculation of the defect vibrations induced in a ZnO:Ni crystal by the Ni+2 impurity. The computations are done by a recursive method in the shell model. Based on the model calculations, the vibronic structure in the absorption spectra of the intracenter d-d transitions in the ZnO:Ni crystal is interpreted.

Local structure and lattice dynamics of alkali halide crystals with an anion vacancy

The local structure and vibrations in the region of an anion vacancy are studied using the pair interionic potentials within the shell model for crystals Me+Cl− (Me+ = Rb+, K+, Na+). The pair potentials are derived from first-principles calculations of different clusters by the Hartree-Fock-Roothaan method with the one-electron states constructed in the form of molecular orbitals as linear combinations of atomic orbitals (MO LCAO). The calculations are performed with the GAMESS program package (US). The correlation corrections are included in the calculations. The validity of the model parameters is verified by comparing the calculated with experimental structural and dynamic properties of ideal alkali halide crystals.

Simulation of the lattice dynamics of an Al-Cu-Fe icosahedral quasicrystal

The total and partial vibrational spectra of aluminum, copper, and iron atoms in an Al-Cu-Fe icosahedral quasicrystal are calculated by the recursive method. The calculations are based on the 1/1 crystal approximant. The interaction of atoms in the Al-Cu-Fe quasicrystal is described within the EAM model. The calculated spectra are in satisfactory agreement with the experimental data on neutron inelastic scattering.

The origin of localized vibrations in KI: Cl and KI: H crystals

The resonant, gap, and local vibrational modes of Cl and H impurities in KI crystals are calculated recursively using the shell model. The contributions from ions located in various coordination shells around the impurity to the formation of localized vibrations are studied. The results of the calculations are in satisfactory agreement with the experimental data.

Ab initio calculations of the structure and dynamics of perfect and imperfect MeF crystals (Me = Rb, K, Na)

The parameters of the F−-F− and Me+-F− pair potentials (Me = Rb, K, Na) are determined from ab initio calculations using the Hartree-Fock-Roothaan method in which one-electron states are described by molecular orbitals formed from linear combinations of atomic orbitals. Nonempirical potentials are used to calculate the structure and dynamics of perfect and imperfect alkali halide crystals. The effect of an anion vacancy on lattice dynamics is studied using the recursive method. It is shown that an adequate description of an imperfect crystal requires consideration of a defect region with ∼1000 ions.

The ab-initio calculation of crystal structure and lattice dynamics of perfect and defective MeX (Me+ = Rb+, K+, Na+; X-= F-, Cl-)

In this work, the interionic pair potentials X-- X-, Me+- X-(Me+ = Rb+, K+, Na+; X- = F-, Cl-) within the framework of shell model were obtained using the self consistent field Rhoothaan-Hartree-Fock approximation allowing the correlation correction in second order Moller-Plesset form. Further, nonempirical pair potentials were used for the calculations of the structure and lattice dynamics of perfect and imperfect alkali halides crystals. Impact analysis of anion vacancies influence on crystal vibrational spectrum was carried out with the help of recursive technique calculations of symmetrized and localized density of vibrational states in the perfect and vacancies including crystal.