Investigations of Bijvoet Differences and Anharmonicity in Gallium Phosphide

Precise X‐ray diffraction intensity data are collected at 300 K using a perfect single crystal sphere of gallium phosphide. The data are firstly analysed assuming a harmonic thermal vibration of atoms. The refined Debye‐Waller factors for this harmonic model are B (Ga) = 0.446(0.010)× 10 −2 nm 2 and B (P) = 0.507(0.001) × 10 −2 nm 2 with the residual index R = 1.2715%. Then anharmonic thermal vibration effects are included in the structure factor expressions. In the anharmonic model, two additional parameters, the individual anharmonic thermal parameters, are also included in the refinement process. The refined values are β(Ga) = −1.201(0.371) × 10 −13 J nm −3 and β(P) = 2.002(0.274) × 10 −13 J nm −3 with R = 1.2646%. The effect of anomalous dispersion on the structure factor is also analysed. It leads to Bijvoet differences between all odd index inverse reflections. The inclusion of anharmonic effects leads to Bijvoet differences between all even index inverse reflections. The measured Bijvoet ratios are in good agreement with the calculated Bijvoet ratios both in sign and magnitude. The individual Debye‐Waller factors, the Bijvoet ratios, observed and calculated both, for the harmonic and anharmonic models, are reported.