LATTICE-DYNAMICS OF ALKALI-METALS IN A 3-BODY INTERACTION

The original model of Das et al. is modified in extending the electron -ion interaction on a three-body forces and including the crystal equi librium condition to reduce one independent parameter. We studied the phonon dispersion relations along the three principal symmetry directi ons i.e. [xi, 0, 0], [xi, xi, 0] and [xi, xi, xi] and theta-T curves o f alkali metals, Na, K, Rb, Cs and Li. There is close agreement betwee n the computed results and the experimental observations.