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 ${\ensuremath{\beta}}_{x}$ in the regime where thermal vacancies are numerous. Comparison of ${\ensuremath{\beta}}_{x}$ 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 ${(\frac{\ensuremath{\partial}P}{\ensuremath{\partial}T})}_{V}$, ${(\frac{\ensuremath{\partial}{B}_{T}}{\ensuremath{\partial}T})}_{V}$, and ${\ensuremath{\chi}}_{T,x}$, the x-ray isothermal compressibility, with a substantial improvement in accuracy over those obtained by purely macroscopic means.

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