Determination of thermal‐motion parameters using energy‐dispersive powder diffraction

An intrinsic Ge detector is used to analyze the energy spectrum of a well collimated X‐ray beam of white radiation diffracted from powder samples of Al, Mg and Ti. Two spectra on each sample are measured at scattering angles where reflections hkl and 2 h ′ 2 k ′ 2 l occur at the same energies. The Bragg reflections are separated by fitting a model for the different components of scattering to the total spectrum. The thermal‐motion parameter B is determined from the intensity ratio of several pairs of reflections. Most of the uncertainties due to a non‐ideal sample or errors in the experimental parameters cancel out in the expression for B . The values of B are 0.86 (2) Å 2 for Al, B a = 1.29 (8) Å 2 and B c = 1.60 (9) Å 2 for Mg and B a = 0.63 (4) Å 2 and B c = 0.73 (7) Å 2 for Ti, where B a is for directions perpendicular to the c axis and B c for the direction of the c axis. The results are in agreement with published values of the thermal‐motion parameters.