e, fcc solid solution: we have taken Ni3Al and a Au solute in copper as examples of these systems. Many-body interatomic potentials for these alloys have been used, but modified at small separations to provide suitable descriptions of collisions at near-threshold energies. The properties of point defects associated with a single Au solute atom in a copper matrix are presented, and it is then shown that the threshold energy, Ed, for the Au recoil in this alloy is smaller and has much less orientation-dependence than is found for a Cu recoil in the pure metal. This effect is related to the number of atoms temporarily displaced from their sites during the creation of a stable Frenkel pair. Ed for Al in Ni3Al is much higher than in pure aluminium and similar in size to that of a Ni atom. The stable defect arrangements produced at threshold are in general much more complex than for pure metals, and defects on the Ni sublattices are usually the majority species. A striking effect occurs for 110 recoils along mixed Ni-Al-Ni-Al- … rows, for chains of antisite defects created by replacement sequences break to form two Frenkel pairs for each primary recoil atom.

On the basis of a new physical picture universally valid for all condensed matter of the infrared-divergence theory and starting from a non-Markovian process, the author investigates electronic excited-state or exciton transfer in disordered systems. The obtained results indicate that the present picture, which differs from the traditional Markovian-transport picture, is more reasonable and more universal than other existing theories. The theoretical predictions are in good agreement with the experimental investigation.

In this paper, a novel waiting-time distribution function (WTDF), ψ(t), which is not purely ex- ponential and is universally valid for explaining recently the low-frequency (say, w<10GHz) fluc- tuation, dissipation, and relaxation properties of condensed matter, is used to discuss asymptotic solutions of the continuous-time random-walk (CTRW) problems. Many results of theoretical and experimental interest are obtained. These results include the mean displacement, the dispersive mobility, the mean-squared displacement, the dispersive diffusion coefficient, the Nernst-Einstein relation, the variance and the standard variance, the lattice statistics, the initial-site occupation probability, the dispersive conductivity, the dispersive electrical transport, and the memory func- tion. All results show that the CTRW process described by the WTDF (t) appears to be non- Markovian over the very broad time domain and is Markovian only in the long-time limit; in oth- er words, all results contain a single parameter n, the infrared divergence exponent, which depends on the microscopic structure of condensed matter and governs the degree of dispersion. The larger the value of n, the stronger the dispersion. When n=0, the dispersion disappears and all results reduce immediately to the classical Markovian forms. This is in agreement with some ex- perimental facts.

A soluble, but nontrivial, model of a dilute Ising ferromagnet is studied, with infinite-range in- teractions but finite average connectivity c. The density of (Yang-Lee) zeros of the partition func- tion in the complex z=exp(-2H) plane (where H is the external magnetic field in units of the tem- perature) is calculated explicitly in the high-temperature phase for large but finite c and small ]H]. The density of zeros on the unit circle H=iO has the form p(θ)～exp{-[cf(K)/]θ]ln( 1/[θ]for [01 >0. The function f(K) (K=J/73 vanishes at the critical coupling Kc(c). Heuristic arguments are given for the form of p(θ) expected for systems with short-range interactions.

In this paper, the effects are examined of the upper and the lower sulface recombinationv elocities, SI,S z, the diffusion length of excess minority carriers, L, and the thickness of the sample, h. on the minority carrier concentration profile (MCCPa) nd on the intensity of cathodoluminescence (CL) from thin foils. A systematic theoretical investigation of these effects is essential lo the understanding of experimental resuits which have recently been obtained by high-resolution CL imaging studies. By solving the reduced one-dimensional steady-stale diffusion equation under the non-trivial and realistic boundary conditions that the recombination velocities SI and Sp on the upper and lower surfaces are allowed lo vary independently of each other, exact and anaiyiical expressions for the MCCP and CL intensity (cu) are oblained for the general case of sulface recombination (sR). A number of special SR cases are discussed. The important question of the thickness dependence of the CL is addressed. Conditions for linear, square or cubic dependence of cu on h are deduced together with expressions for a thickness which we call the cut-off thickness. The capability of using the present analytical resun for MCCP to treat the electronbeam- induced current problem here is pointed out in passing together wlh TEM or STEM charge collection imaging and contrast problems of dislocations or defects. Specific numerical calculations are used to display the theoretical resuits quanlilalively and reveal a variety of properties of the model controlled by different values of the parameters contained within it. The resuits obtained can be used to explain and examine the features of CL in thin-film materials when examined in TEM or STEM modes. in some given cases, experimental determinations of the parameters can be made: