scispace - formally typeset
Search or ask a question

Showing papers by "Ternopil Ivan Pul'uj National Technical University published in 2000"


Journal ArticleDOI
TL;DR: In this paper, the possibility of defect structure and strain control using nanosecond laser irradiation-induced shock waves (LSW) both in bulk materials and at the interfaces is investigated.
Abstract: The possibility of defect structure and, consequently, strains control using nanosecond laser irradiation-induced shock waves (LSW) both in bulk materials and at the interfaces is investigated. The conditions of the experiment are selected to ensure that the main result of the LSW action would be a change of defect structure at a significantly larger depth in comparison with a thermal influence region. The influence of weak LSW on Fe-Mo and Si–SiO2 interfaces is considered. The potentiality of this technique with respect to the structural quality and residual strains of (Hg, Cd)Te solid solutions due to the LSW interaction with extended defects (low-grain-boundaries, precipitates, etc.) is demonstrated.

13 citations


Posted Content
TL;DR: In this article, the electron correlations in narrow energy bands are examined in framework of the Hubbard model and the singleparticle Green function and energy spectrum are obtained in paramagnetic state at half-filling by means of new two-pole approximation.
Abstract: The electron correlations in narrow energy bands are examined in framework of the Hubbard model. The single-particle Green function and energy spectrum are obtained in paramagnetic state at half-filling by means of new two-pole approximation. In the ground state analitical expressions for the energy gap, polar states concentration and energy of the system are found. Metal-insulator transitions in the model at change of bandwidth or temperature are investigated. The obtained results are used for interpretation of some experimental data in narrow-band materials.

4 citations


Posted Content
TL;DR: In this paper, the ground state energy and condition of ferromagnetic state realization were found using the Green function technique in the case of weak electron-electron interaction and correlated hopping in the partially filled narrow band.
Abstract: In the present work ferromagnetic ordering in the Hubbard model generalized by taking into account the inter-atomic exchange interaction and correlated hopping in partially filled narrow band is considered. In the case of weak electron-electron interaction the ground state energy and condition of ferromagnetic state realization are found using the Green function technique. The obtained results indicate the important role of correlated hopping.

3 citations


Posted Content
TL;DR: In this article, a two-pole approximation of the transition from an insulating state to a metallic one at increase of bandwidth, and also the observable in some compounds transition from a metalic state to an increasing temperature with increasing temperature, is presented.
Abstract: A new two-pole approximation, which allows to describe the transition from an insulating state to a metallic one at increase of bandwidth, and also the observable in some compounds transition from a metalic state to an insulating one with increasing temperature, is presented. The case of a paramagnetic narrow-band material at half-filling is considered. Single-particle Green function and energy spectrum of electron system are calculated. The expressions for energy gap width and the concentration of polar states (holes or doublons) are obtained. The conditions for metallic and insulating states are found.

1 citations


Posted Content
TL;DR: In this article, a pressure-temperature phase diagram of a generalized Hubbard model with correlated hopping in a paramagnetic state at half-filling is determined by means of the generalized mean-field approximation in the Green function technique.
Abstract: In the present paper pressure-temperature phase diagram of a generalized Hubbard model with correlated hopping in a paramagnetic state at half-filling is determined by means of the generalized mean-field approximation in the Green function technique The constructed phase diagram describes metal-to-insulator transition with increasing temperature, and insulator-to-metal transition under the action of external pressure The phase diagram can explain paramagnetic region of the phase diagrams of some transition metal compounds We have found that taking into account correlated hopping allows much better description of these experimental data than the Hubbard model; this testifies also much better physics of the present model and the important role of correlated hopping