Title: ATOMIC STATIC DISPLACEMENTS AND THEIR EFFECT ON THE SHORT RANGE ORDER IN ALLOYS
Authors: Z.Gurskii, Yu.Khokhlov (Institute for Condensed Matter Physics, National Academy of Sciences of Ukraine, 1 Svientsitskii St., UA-290011 Lviv, Ukraine)

The influence of local atomic static displacements (ASD) on the short range order formation in binary alloys is investigated within the microscopic theory. Explicit expression for the binary correlation function Fourier components $\langle \rho_{{\bff k}}\rho_{-{\bff k}} \rangle$ is obtained by the collective variables method. The theoretical results are illustrated by numerical calculations performed for disordered alloys of the K-Cs and Ca-Ba systems. A drastic effect of the ASD on the $\langle \rho_{{\bff k}} \rho_{-{\bff k}} \rangle$-function behaviour in the first Brillouin zone is observed. The ASD smooth the dispersion of the $\langle \rho_{{\bff k}} \rho_{-{\bff k}} \rangle$-function. Negative values of the short-range order parameter on the first coordination sphere indicate a trend to the ordering in alloys of the systems investigated. The ASD are shown to favour the ordering tendency. The theoretical conclusions concerning the temperature influence on the short range order parameter perfectly agree with the experimental data from the treatment of the X-ray diffuse scattering in binary alloys.

Key words: atomic static displacements, short-range order, disordered alloy, binary correlation function, free energy
Comments: Figs. 6, Refs. 11, Tabs. 2.