Neutron Diffraction Determination of Mean-Square Atomic Displacements.

摘要

Integrated intensities for Bragg reflection of neutrons from single crystals of the III-V compounds, InAs and GaSb, have been measured at room temperature. The data were collected at two wavelengths, 0.947 A and 1.241 A, in order to establish the adequacy of a correction for moderate to severe anisotropic extinction. Data were also obtained for InAs at four temperatures from 408 K to 933 K. Corrections for thermal diffuse scattering were applied. The results were analysed in the one-particle potential approximation with terms to fourth-order in the atomic displacements u = (u sub 1 , u sub 2 , u sub 3 ). At 296 K, the mean-square components were determined for In, 0.0116(2)A exp 2 and As, 0.0102 (1)A exp 2 ; for Ga, 0.0120(3)A exp 2 and Sb, 0.0107(3)A exp 2 . The third-order coefficients for InAs are comparable with those for Si and Ge, those for GaSb with those for zinc chalcogenides. Non-harmonic behaviour in InAs is observed below 400 K. (Atomindex citation 12:615191)