Diffuse X‐Ray Determination of the Energy of Mixing and Elastic Constants of GeSi Solid Solutions

The short‐range order and elastic properties of GeSi solid solutions of 28, 54, and 64% Si are studied by means of X‐ray diffuse scattering measurements. The mixing energy of the system taking into account the existence of two f.c.c. sublattices in the diamond structure is determined by extrapolating the long‐wave Fourier transforms of the concentration fluctuations Cq to q = 0 points corresponding to the node (400) and equals for q = 0 to W(q=o) = (2.5 ± 0.2) kcal/mol. The elastic constants of the GeSi solid solutions are determined and their positive deviations obtained from the additive values which are in good agreement with the data of the lattice parameter of the system.