Thermal Expansions of Solid Argon, Krypton, and Xenon above 1 K

A differential parallel-plate capacitance dilatometer has been used to measure the linear thermal-expansion coefficients of free-standing samples of solid argon (1-35 K), krypton (1-45 K), and xenon (1-105 K). The present data for argon and krypton are systematically larger than existing x-ray lattice-parameter data above 20 K by a constant proportionality factor which varies from 1 to 3% for different runs and different samples and which most likely is due to bonding of the samples to the capacitor plates. These data have been normalized using the x-ray results. The xenon results agree with other published data without the use of a scale factor. Temperature-dependent Grüneisen parameters $\gamma$ are calculated for these solids using available thermodynamic data. These calculations give ${\gamma }_0=2.7\mathrm{}\pm 0.1$ for argon, 2.67 ± 0.07 for krypton, and 2.5 ± 0.1 for xenon, with the major uncertainty occurring through the bulk-modulus data.