Elastic Constants of hcpHe4

Experimental values for the elastic constants of hcp ${\mathrm{He}}^4$ are derived from longitudinal sound velocities and the compressibility. The derivation makes use of a relation between the elastic constants which is a consequence of the volume independence of the axis ratio of hcp ${\mathrm{He}}^4$. Good agreement exists between the elastic and calorimetric Debye temperature.