Strain-Induced Effects on Interactions of Non-Metal Atoms Introduced Metals Having H.C.P. Structure. 1. Interstitial Atoms on Octahedral Interstices

摘要

We consider the analytic peculiarities and singularities of various interactions between non-metal atoms of X (X = 0, N, C, H) located at octahedral interstices in an h.c.p. metal Me (Me = #alpha#-Be, #alpha#-Ti, #alpha#-Zr, #alpha#-Hf, #epsilon#-Fe, Tc) taking into account its discrete structure, anisotropy of elasticity, and 'size' effect. The interaction between X atoms, caused by distortions they induce into the h.c.p. Me, is studied by the lattice statics method in a quasi-harmonic approximation; the microscopic parameters of their 'direct' interactions are estimated using semiempirical approximations. It is shown that the energy of an 'orderable' h.c.p.-Me-X (#alpha#Be-O, #alpha#Ti-C, #alpha#Ti-N, #alpha#Ti-O, #alpha#Zr-N, #alpha#Zr-O, #alpha#Hf-O, Tc-H, Tc-C, #epsilon#Fe-N) solid solution in (meta)stable single-phase states cannot be estimated adequately without taking into account the strain-induced interaction between X atoms as an additional contribution to their 'electrochemical' interaction. The results of calculation indicate, e.g., a tendency of the #epsilon#Fe-N alloy to form, generally speaking, nonstoichiometric phases of the #epsilon#-Fe_3N, #epsilon#-Fe_2N, and #xi#-Fe_2N types (that have been studied by Jack et al. (6, 53-55)) which show superlattice reflections in diffraction patterns in the special points K (middles of the vertical edges of the first Brillouin zone) or M (centres of the rectangular faces of the first Brillouin zone) of the reciprocal space of the h.c.p. lattice of sites. Besides, for instance, the h.c.p.-Tc-H solid solution tends to decompose into two phases distinctive in concentrations, and, evidently, its anti-CdI_2-type 'orientationally' ordered phase (detected by Glazkov et al. (44)) is intermediate and metastable.