Thermal expansion and bulk modulus of cobalt

The ten third-order elastic (TOE) constants of hexagonal cobalt, which has nearly the ideal c/a value, have been evaluated using the nearest-neighbor central interaction model for hexagonal materials proposed by Ramji Rao and Srinivasan. These TOE constants have been employed to evaluate the low-temperature limit {Mathematical expression} of the thermal expansion, the Anderson-Grüneisen (AG) parameter δ, and the second Grüneisen constant q of cobalt. {Mathematical expression} has the value 2.08 for cobalt. The temperature variation of the volume Grüneisen gamma of cobalt has been calculated on this model. The high-temperature limit {Mathematical expression} has the value 2.13, which agrees well with the experimental value obtained from thermal expansion and specific heat data of cobalt. Anderson's theory has been used to explain the temperature dependence of the bulk modulus of cobalt and compared with the experimental values obtained from the elastic constant data of Fisher and Dever. The calculated Bs values agree with the experimental values to within 1%. © 1977 Plenum Publishing Corporation.