Atomic Size Effect in the X-Ray Scattering by Alloys

Abstract

In a random solid solution, if the two atoms have appreciably different sizes, the nearest‐neighbor distances and to a lesser extent the higher neighbor distances will be of three kinds, γ_AA, γ_AB, and γ_BB. The effect produces modulations in the diffuse intensity similar to those produced by short‐range order. The size effect is important when the difference in scattering power is large, the difference in size is large, and the short‐range order is small. The size effect is illustrated by a single crystal pattern of Cu₃Au and a powder pattern of Ni₃Au₂. An asymmetry in the wings about a fundamental reflection is a result of the size effect.