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R. Eggenhoffner C.S.N. Murthy F.G. Fumi 《Journal of Physics and Chemistry of Solids》1978,39(12):1295-1299
Some comments are presented on three phenomenological potentials for the alkali halide crystals proposed in recent years by Narayan and Ramaseshan, by Woodcock, and by Romano, Margheritis and Sinistri. In the context a brief comment is made on the van der Waals coefficients reported by Hajj. 相似文献
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The first results of a systematic study of interatomic potentials in sixteen alkali halides derived using the hybrid Thomas-Fermi-Dirac method are presented. Both the basic method and modifications to (a) correct the exchange energy to exclude the self-exchange part and (b) scale the kinetic and exchange energy terms are employed. The interactions between ion pairs are calculated at a set of interionic distances in a range corresponding to ± 30% deviations from the appropriate measured equilibrium separation. In this way a tabular function for the lattice energy/ion pair is constructed and predicted values of the equilibrium nearest neighbour interionic distance, the equilibrium lattice energy/ion pair and the Smith stiffness parameter are found numerically. The derived short-range interactions between ion pairs are fitted over the whole range to the analytic form A exp() + CR?6. It is shown that the use of an expression for the lattice energy/ion pair involving these analytic forms introduces significant errors in the predicted physical parameters. 相似文献
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The colour-induced magnetic dipole interaction between hadrons is discussed. Fermion motion in a gauge field obtained by solving the classical Yang-Mills equations is considered. It is shown that the spectrum of stationary fermion states is discrete and bound states are colourless. The long range asymptotic behaviour of the gauge potential results in the van der Waals interaction of hadrons. 相似文献
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The van-der-Waals version of the second virial coefficient is not far from being exact if the model parameters are appropriately chosen. It is shown how the van-der-Waals resemblance originates from the interplay of thermal averaging and superposition of scattering phase shift contributions. The derivation of the two parameters from the quantum virial coefficient reveals a fermion-boson symmetry in non-ideal quantum gases. Numerical details are worked out for the Helium quantum gases. 相似文献
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A perturbation method used previously to calculate rare-gas potentials for He2 and Ne2 is modified to handle the many contributions to the Coulomb and exchange energy for heavier atoms. The procedure involves a transformation to an equivalent orbital basis and the neglect of all except the largest overlap contributions to the energy. Potentials are obtained for homo- and heteronuclear pairs for the atoms He, Ne and Ar, and the results are compared with the best empirical potentials. 相似文献
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R.B. Yadav 《Solid State Communications》1983,46(4):341-342
A new repulsive term in the ionic interaction potential ψ(r) = Ar?ne?r/gl, is suggested and the three unknown parameters A, λ and n are evaluated. Lattice energies of alkali halide crystals are calculated using this form. The results agree fairly well with the experimental values. 相似文献
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It is shown that the metallization of a dielectric in the region of its interaction with laser radiation is a substantiated mechanism of laser damage of wide-gap dielectrics. Calculations of the radiation pressure produced by high-power laser radiation and the pressure of external bulk compression at which the dielectric energy-gap width becomes zero and which is calculated on the basis of the self-consistent statistical electron theory of ionic crystals have shown that these pressures are of the same order of magnitude. 相似文献
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The Debye temperature D is calculated from the elastic constants for 18 alkali halide crystals. Comparison of the results with calorimetric data D reveals an agreement within the experimental error. The temperature dependence of D is determined for NaCl, NaBr, KCl, and KBr crystals from the elastic constants, and this dependence is compared with the calorimetric data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 3, pp. 89–94, March, 1971. 相似文献
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Nonparametric equations of state are obtained for NaBr, KBr, RbCl, and RbBr crystals with B1 and B2 lattices over a wide pressure range. Binding energy, lattice parameters, and free crystal compressibility are calculated together with phase-transition pressures and volume change on transition from B1 to B2 lattice. Calculated results agree well with experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 101–105, January. 1976. 相似文献
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Jianing Han 《Molecular physics》2020,118(1)
We report on the six-body van der Waals interactions within Rydberg atoms. Specifically, we focus on the octahedron case. The results are compared with previous calculations for two to five bodies' interactions. This research is useful for crystal structure in condensed matter physics, such as p-type doping in Silicon or other types of semiconductors. This research is also useful for studying big molecules in chemistry, chemical engineering, and other fields. 相似文献
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The liquid-vapor interface of a confined fluid at the condensation phase transition is studied in a combined hydrostatic/mean-field limit of classical statistical mechanics. Rigorous and numerical results are presented. The limit accounts for strongly repulsive short-range forces in terms of local thermodynamics. Weak attractive longer-range ones, like gravitational or van der Waals forces, contribute a self-consistent mean potential. Although the limit is fluctuationfree, the interface is not a sharp Gibbs interface, but its structure is resolved over the range of the attractive potential. For a fluid of hard balls with –r
–6 interactions the traditional condensation phase transition with critical point is exhibited in the grand ensemble: A vapor state coexists with a liquid state. Both states are quasiuniform well inside the container, but wall-induced inhomogeneities show up close to the boundary of the container. The condensation phase transition of the grand ensemble bridges a region of negative total compressibility in the canonical ensemble which contains canonically stable proper liquid-vapor interface solutions. Embedded in this region is a new, strictly canonical phase transition between a quasiuniform vapor state and a small droplet with extended vapor atmosphere. This canonical transition, in turn, bridges a region of negative total specific heat in the microanonical ensemble. That region contains subcooled vapor states as well as superheated very small droplets which are microcanonically stable. 相似文献
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Soji Miyagawa Kenji Morita Noriaki Matsunami Kazuya Tachibana Noriaki Itoh 《辐射效应与固体损伤》2013,168(3-4):271-276
The effects of the lattice distortion in KCI-KBr mixed crystals on the dechanneling of 1.5 MeV protons are studied by means of backscattering. The dechanneling rate vs. the composition curve has a maximum at about 1:1 mixture of KCI and KBr. The lattice distortion in the mixed crystals is estimated from the dechanneling rate, and the result agrees well with that obtained by an X-ray measurement. The effective cross-section for the dechanneling caused by the lattice distortion is obtained, and compared with the results of a calculation based on a simple model. 相似文献
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Yu. I. Tyalin V. A. Tyalina V. A. Fedorov M. V. Chemerkina A. A. Butyagin 《Physics of the Solid State》2004,46(9):1667-1670
The healing of micro-and macrocracks under local heating and x-ray irradiation of LiF single crystals is studied. The main features revealed in crack healing due to local actions are described. The contribution of the plastic zone formed upon the arrest and healing of a crack to the strength of the crystal is estimated. 相似文献
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Microhardness measurements done in KCl, KBr and in different compositions of KCl-KBr mixed crystals show that it varies nonlinearly
with composition. In order to investigate the nature of defects, several techniques such as etching, ionic conductivity and
dielectric loss have been employed which showed that the mixed cristals of KCl-KBr are more defective, containing a high concentration
of dislocations, low-angle grain boundaries and vacancies as compared to the end products KCl and KBr. These imperfections
appear to be responsible for the nonlinear variation of microhardness in mixed crystals. The microhardness studies also revealed
that the difference in size of the ions constituting the mixed system are responsible for the internal strains which in turn
give rise to imperfections affecting the microhardness of mixed crystals. 相似文献
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Measurements of self diffusion coefficients of 42K, 85Rb and 125I and measurements of ionic conductivity were carried out on single crystals of the (Rb2K1-Z)I solid solutions (z varying from 0 to 1). The self-diffusion coefficient measurements (T=875 K) indicate that two types of cation have the same mobility and that this mobility is about twice that of the anion. All these mobilities are higher for the solid solutions than for the pure components, KI and RbI. The ionic conductivity was analysed using the Schottky defect model. Interactions between defects were taken into account in this analysis. Thus, enthalpies and entropies of formation and migration of vacancies were determined. Examining the variations of these parameters as functions of composition z at a given temperature shows that the density of vacant sites is significantly higher in the case of solid solutions than in the case of pure components (for example, this density is about twice as large for (Rbo.sK0.5)I as for KI or RbI). 相似文献