Vacancies in Solid Argon

The enthalpy and entropy of vacancy creation in solid argon are re-evaluated using the two-body force approximation. At the triple point, the resulting vacancy free energy is g, = 1900 -4.0 RTcaljmole vat. This does not agree well with previous calculations of g,, but agrees well with experimental values of g, obtained from the argon specific heat”’ C, (but not with the questionable values obtained from CJ and with direct measurements (r3) of (n/N) = exp( -gJRT). If the present value of g, is correct, the agreement with experiment suggests that many-body effects contribute little to the binding of argon atoms around a vacancy.