The elastic constants for hcp solid ${\mathrm{He}}^4$ recently published by Crepeau, Heybey, Lee, and Strauss are used for calculating the wave surfaces associated with elastic waves, according to the recent method of Wanner. The deviation of the energy path or ray from the wave normal is calculated and is correlated with experimental sound-velocity data previously obtained by the authors.

• Received 7 January 1972

DOI:https://doi.org/10.1103/PhysRevA.6.516