For pt. I, see ibid., vol.7, no.18, 3260 (1974). A detailed study is undertaken of the physical mechanism underlying the quasi-harmonic lattice dynamics of the rhombohedral lattice model with nearest-neighbour central force interactions. The study provides both a formal and a conceptual understanding of the behaviour of the normal mode frequencies, directions of polarization and Gruneisen parameters. The anisotropy of the model can be varied and its effect on the microscopic vibrational properties is elucidated. As examples, results are presented for two extremes of anisotropy, together with results for the special case of cubic symmetry.