Specific Heat and Other Thermodynamic Properties of Body-Centered-CubicHe3

Abstract

The heat capacity of bcc ${\mathrm{He}}^3$ has been measured between about 0.4°K and the melting curve. The results are in excellent agreement with the recent specific-heat measurements of Sample and Swenson, and the two sets of data have been used to calculate the entropy, the pressure coefficient ${\left(\frac{\partial p}{\partial T}\right)}_V$, and, in conjunction with melting-curve data, the internal energy at melting and at 0°K. The values of ${\left(\frac{\partial p}{\partial T}\right)}_V$ are in excellent agreement with direct measurements except in a small temperature interval close to the melting curve. The internal energy at 0°K, $\frac{U_0}{R}$, ranges from -1.05 deg K at 24.0 ${\mathrm{cm}}^3$/mole to +1.93 deg K at 20.0 ${\mathrm{cm}}^3$/mole, and is about 4 deg K below the theoretical values of Koehler and Horner and about 1.0 deg K below those of Hansen and Levesque. Measurements of the discontinuous change in heat capacity on melting have been used to obtain values for the compressibility of the solid which are in good agreement with those from other methods and which range from 4.8×${10}^{-3\mathrm{}}$ ${\mathrm{atm}}^{-1\mathrm{}}$ at $V=23.5\mathrm{}$ ${\mathrm{cm}}^3$/mole at 1.75×${10}^{-3\mathrm{}}$ ${\mathrm{atm}}^{-1\mathrm{}}$ at $V=19.7\mathrm{}$ ${\mathrm{cm}}^3$/mole.