On the interlattice displacement of rhombohedral structure

The expressions for the components of the interlattice displacement to the first order in strain and hence the expressions for the SOE constants are obtained for the rhombohedral lattice using the method of homogeneous deformation. Two and three body interactions are considered up to fourth neighbours in the calculations. The special strains that are generally chosen in explaining the temperature variation of thermal expansion of a uniaxial crystal, which make the interlattice displacement zero, are shown to be dependent [ηzz = - 3 2p2 C D (ηxx + ηyy)]. The internal displacement factors A, B, C and D are calculated for the metals As, Sb and Bi to get an idea on the magnitude of C/D. © 1979.