In this paper we study Maradudin's recent approximation to the complex manyhyphen;body expression for the quartic anharmonic contributionF4to the free energy of a facehyphen;centered cubic crystal. It turns out that one can calculateC4, the quartic anharmonic contribution to the specific heat corresponding toF4, almost exactly at any arbitrary temperature by use of the vibration spectrum, thus necessitating only a single summation over the Brillouin zone. The machinehyphen;calculated result is an accurately determined curve ofC4/Char, whereCharis the harmonic specific heat, for a lattice model chosen to represent copper. This curve shows structural features in the form of wiggles and in the discussion it is argued that the cubic anharmonic contributionC3/Charwould not negate the structure ofC4/Charin the total form of the anharmonic contribution to the specific heat (C3+C4)/Char. Consequently, the theoretical results are compared with the experimental specific heat of copper expressed in the formCLT, V(0deg;K)/Char, whereCLdenotes the experimental lattice specific heat remaining after the necessary thermodynamic corrections have been made. Certain features of the experimental curve agree with the structural features ofC4/Charalone, despite the fact thatC3/Charis not presently taken into account.
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