Density-functional approach to charge-transfer insulators

Self-consistent density-functional calculations have been carried out for Ag-row impurities in Cs within the spherical solid model. The results for the electronic structure provide an account of the observed resistivity, susceptibility and spin-flip scattering behaviour.     

Density-functional approach to two-dimensional classical fluids

The density-functional (DF) method is combined with the smoothed-density approximation to calculate the fluid structure in two-dimensional (2D) hard-disc (HD) systems. Density-dependent weighting functions in the DF method proposed by Tarazona for three-dimensional fluids have been applied to 2D systems for the calculation of the radial distribution function of HD fluids and the determination of the static structure of 2D HD fluids around the central hard triatomic molecule. The results compare reasonably well with Monte Carlo data. The radial distribution of a 2D Lennard-Jones fluid has also been calculated and shown to be in satisfactory agreement with Monte Carlo data except for the high-density fluid.     

Structure-mechanical approach to surface tension of solids

Some problems of applying the Lippmann equation to adsorption studies on solid electrodes are shortly reviewed. A novel nonthermodynamic approach to consider the role of elastic and plastic deformation of electrode surfaces during adsorption is proposed. The extremely thin electrode surface layers affected electrically and mechanically by adsorbate are supposed to be free of dislocations because of volume discrepancy. The nearest structure-mechanical analogs of such layers are the whisker crystals whose side surface could have one- and two-dimensional defects, but have no active dislocations. Like whiskers, surface metal layers should possess a high ultimate strength close to the theoretical one and a purely elastic deformation. Affected only by adsorbate, the surface electrode layer should be considered as absolutely elastic body, whose plastic deformation is impossible, i.e. the Lippmann equation and other equations containing terms of plastic deformation cannot be used in thermodynamics of the solid metal surface.     

Transport phenomena in superionic solids: Master equation approach

A first-principles derivation of the master equation is systematically given based on Kikuchi's ansatz, which is then applied to non-interacting (ideal) and interacting lattice–gas systems. The former application to an anomalous diffusion, observed by MD simulation of β-AgI, makes its mechanism clear in terms of relaxation modes such that the anomalous diffusion is due to non-diffusive (collective) modes. It is also shown in random systems that anomalous frequency-dependent conductivities, made up of Jonscher and nearly constant loss regimes, are reduced to a single master curve. The case of interacting lattice–gas system is discussed on the ab-plane of Rb₃H(SeO₄)₂ by a pair approximation of the path probability method, where a spontaneous strain involved in the ferroelastic phase turns out to be a proton-trapped state originated in an attractive strain energy mediated by a proton–displacement interaction, and the transition to superprotonic phase is due to an off-trapping of protons. This mechanism is confirmed by no phase transition without the attractive strain energy.     

Green’s function approach to phonon hydrodynamics in solids

In the first part the Green’s function approach developed byKadanoff andBaym is used to derive a transport equation for phonons in a dielectric anharmonic crystal. The approximations which reduce this generalized equation to the Peierls equation are exhibited. In the second part, neglecting Umklapp processes, the linearized equation is applied to hydrodynamic phenomena. In a system close to local thermal equilibrium second sound and Poiseuille flow may exist. The damping through normal processes is approximately calculated by a momentum-dependent relaxation time. The coupling between the phonon and the dilatation fields is discussed.     

A mesoscopic approach to point-defect clustering in solids during irradiation

Accumulation of point defects in solids during irradiation is often accompanied by self-organization processes which lead to point-defect clustering and thus to the formation of a spatially inhomogeneous defect structure. Within the framework of a mesoscopic phenomenological approach, the conditions for clustering of mobile point defects caused by their elastic interactions are studied. It is shown that differences between the elastic interaction of similar and that of dissimilar defects may lead to such clustering. Further, it is shown that the presence of impurities acting as traps for interstitials may promote the clustering process. The conditions for spatial clustering are studied for characteristic material parameters in order to predict experimental observations of this phenomenon in metals and ionic solids.