Elastic wave propagation in the group VB semimetals

Abstract

Elastic wave velocities, particle displacement and energy flux vectors are presented and compared for the three rhombohedral, A7 structure, semimetals arsenic, antimony and bismuth. The wave velocity surfaces are discussed in terms of the crystal symmetry. The pure mode axes in each crystal—knowledge of which is especially useful in experimental pulse echo ultrasonic studies—are given. The elastic wave propagation in antimony and bismuth single crystals is shown to differ not only in degree but also in kind from that in arsenic which exhibits the characteristics expected for a layer-like crystal: high, direction insensitive, ultra-sound velocities in the xy plane and lower velocities along the direction ( z) of weakest inter atomic binding. Knowledge of the energy flux and particle displacement vectors has provided a basis for reassessment of the elastic moduli of arsenic at room temperature: C 11=+130·2±1·0, C 12=+30·3±2·1, C 13=+64·3±1·1, C 14=−3·71±0·52, C 33=+58·7±1·0, C 44=+22·5±0·5, C 66=+50·0±1·6 in units of 10 10 dynes cm −2.