Crystalline xenon: Lattice parameters, thermal expansion, thermal vacancies, and equation of state

Lattice parameters of solid xenon have been measured at sublimation in the temperature range 78.2-160.7 K and at melting in the range 161.7-216.0 K. From these precise data, information about (1) thermal expansion and thermal vacancies and (2) thermodynamic and equation-of-state properties can be obtained. Analysis of the sublimation data yields the first determination of the x-ray coefficient of thermal expansion βₓ in the regime where thermal vacancies are numerous. Comparison of βₓ with the coefficient of bulk thermal expansion allows the first experimental determination of the vacancy formation parameters in solid xenon. As is the case for krypton, a significant discrepancy is found between the experimental vacancy formation enthalpy and published theoretical estimates. To obtain thermodynamic and equation-of-state information, the present sublimation and melting lattice parameters are used in conjunction with previously determined sublimation and melting pressures. These data are analyzed to calculate the parameters (∂P∂T)V, (∂BT∂T)V, and χT,x, the x-ray isothermal compressibility, with a substantial improvement in accuracy over those obtained by purely macroscopic means.