Entropy of Binding between Vacancy and Solute in Harmonic Lattices
F. Nakamura, Mitsuo Chikasaki, Jin-ichi Takamura, Shôzô Takeno · Journal of the Physical Society of Japan · 1986
The vibrational contribution to the binding entropy between a vacancy and a solute atom is investigated in the high temperature harmonic approximation. An exact formal expression is derived by the use of the Green's function method and applied to simple model lattices. The formal result reveals that the vibrational entropy change is expressed by the sum of two terms: a mass dependent term, which is not affected by the spatial configuration of defects; and a force-constant dependent term, so that the entropy change on association of defects such as vacancy-solute binding depends only on force constants around the complex but not on the mass. The general feature of the binding entropy between a vacancy and a solute atom is deduced from the numerical calculation of the formal expression for a simple cubic lattice with the nearest neighbour force interaction, and is compared with experimental results.