Lattice Dynamics and Some Related Thermal Properties of Body†Centred Cubic Metals

A phenomenological model is developed for the calculation of the lattice dynamics and thermal expansion of a homogeneously strained body‐centered cubic (b.c.c.) crystal in which both two‐and three‐body interactions are assumed to operate. The phonon dispersion curves and lattice heat capacity of the four alkali metals Li, Na, K, and Rb, and of the three transition metals α‐Fe, Mo, and W are computed employing four second order parameters in each case. The second‐order elastic constants of these metals are also evaluated. The model is then applied to the four alkali metals to calculate their generalised Grüneisen parameters for various normal mode frequencies and hence the temperature dependence of their effective Grüneisen functions. The results of calculations are in good agreement with the corresponding experimental data wherever the latter exist. Copyright © 1981 WILEY‐VCH Verlag GmbH & Co. KGaA