Thermal expansion of trigonal elements at low temperatures: As, Sb and Bi

Linear coefficients of thermal expansion have been measured from 2 to 30 K, 55 to 90 K, and at 283 K for single crystals of As, Sb and Bi inclined at various orientations to the symmetry axis. The principal coefficients alpha /sub /// and alpha perpendicular to and volume coefficient beta are reported, together with the Gruneisen parameters gamma , gamma /sub /// and gamma perpendicular to . The anisotropy of expansion is most marked for As and least for Bi: alpha is negative for As below about 150 K, for Sb below 20 K, but always positive for Bi. beta and hence gamma is positive for each: the limiting value is gamma 0 =4.4+or-0.3 for As, 1.00+or-0.03 (Sb) and 1.9+or-0.1 (Bi). gamma (T) has a minimum at 8 to 10 K, a broad maximum between 20 and 40 K, and at room temperature approaches 1.5 for As and 1.0 for Sb and Bi.