Elastic Constants of LiF from 4.2°K to 300°K by Ultrasonic Methods

The values of the elastic constants of LiF at 4. 2^ are found to be c₁₁=12. 4610^11, c₄₄=6. 4910^11, and c₁₂=4. 2410^11 dynes/cm^2. At 300^ c₁₁=11. 1210^11, c₄₄=6. 2810^11, and c₁₂=4. 2010^11 dynes/cm^2. A Debye characteristic temperature, ₃, has been calculated from these values by using the Houston method of averaging the velocity over different directions in the crystal. At 4. 2^, ₃=734^K in good agreement with the specific heat work of Martin. At 300^, ₃=708^K which is not in good agreement with values derived from specific heat measurements. A model has been suggested in which a combination of Debye and Einstein terms is used in the specific heat theory.