Improved debye-waller factors for some alkali halides

Anharmonic contributions to Bragg diffraction. II. Alkali halides

“…As the statistical errors in the scattering results were too large to determine the magnitude of both the T and T 2 components from a computer fit of the data, it was decided instead to use theoretical values for the harmonic DebyeWaller factors and determine the component in T 2 from a fit of the data, because a number of detailed calculations have been carried out for various harmonic models. The data of Reid & Smith (1970) were chosen for the purpose, and this yielded a smaller value for the m lz parameter for KC1 than had been found in previous experimental or theoretical treatments, suggesting that the m34 term might have been overestimated here, but the values for NaCI tallied reasonably well (Table 2). For KBr (Fig.…”

“…The elastic intensity Isu M can be written in the form: (Reid & Smith, 1970), --.--quasi-harmonic theory, ----including additional T 2 term, • .... with T 2 term found by including terms in T 3.…”

“…The variation in the magnitudes of the anharmonic terms in the different alkali halides allows no simple conclusions and implies that detailed theoretical (Reid & Smith, 1970). potential energy, which tend to cancel in the evaluations, may be finely balanced.…”

Dynamic deformation effects on the Debye–Waller factor

“…The actual ones used were those which the author previously employed in a detailed evaluation of the harmonic Debye-Waller factors (Reid & Smith, 1970, 1971. With a sample of 64 000 modes uniformly covering the Brillouin zone, the essential constant Sk/B k was determined for each ion in six alkali halides (Table 1).…”

Temperature dependence of integrated thermal diffuse scattering

“…In this sense it is the modes at the boundary of the sphere which determine the temperature dependence and not those near the centre. For the calculations, temperature-dependent Debye-Waller factors (Reid & Smith, 1970b) and lattice constants were used at all temperatures. Below room temperature, the temperature dependence of the elastic constants and optic frequencies was also taken into account.…”