Papers by Keyword: Quantum Model

Abstract: The article examines the impact of nanodefects on the reduction of the crystals strength. A summary of the authors research results is illustrated by the analysis example of the NaCl crystal destruction process from the standpoint of strength quantum theory. As the base experiment is seen testing the dry and wet a salt crystal made by academician A. Ioffe. The authors research aim was a little-studied patterns of the crystal lattice destruction quantum mechanism. The article gives a brief historical background of the research in this area. The first section discusses the rystal cell dynamic characteristics change as a result of destruction. Assesses self-resonant frequency of an atom at a lattice point of the crystal before and after the destruction. In the second section of the article examines the relationship between the natural frequencies of the atoms in the lattice and elastic energy wich accumulated in the crystal body in the force loading process. The main attention is paid to theoretical modeling of the links strength between atoms in the crystal surface layer. We study the strength dependence of these relationships to the availability of nanodefects on the crystal surface. There are modeled bond strength to clean the crystal surface, as a result of the surface lattice electrification when atoms capture free electrons and for the case when jobs of atoms in the crack are filled with the external environment atoms. The calculations confirm the validity of the proposed theoretical model of reduction or the hanging of the crystals strength by the atoms interaction with the external environment.

Abstract: The modification of the extended Tao-Eldrup model accounting ortho-positronium quenching in air is presented. Taking into account quenching by oxygen molecules adsorbed on the surface of porous material gives reasonable agreement between results of the model and the experimental positron annihilation lifetime spectroscopy data. Pore size distributions calculated using this model from the spectra for MCM 41 mesoporous sieve obtained in air, oxygen or vacuum are compared and discussed taking into account effect of ortho-positronium migration from small open pores to the larger ones. The rates of ortho-positronium quenching by air (47.2 µs-1 MPa 1), oxygen (220 µs-1 MPa-1) or nitrogen (1.7 µs-1 MPa-1) obtained from pressure dependences of the lifetimes observed in MCM 41 agree reasonably with the experimental results of other authors, if the correction for oxygen adsorbed on the surface is applied.