Calculating grain boundary energies and other defect energies in ordered alloys

摘要

The calculation of the excess free energy of a grain boundary, a surface or a dislocation core in a material requires: (a) calculation of the free energy of a large region containing the defect, and (b) subtraction of the sum of the chemical potentials of each of the atoms within the region. The result in an ordered alloy depends critically on exactly how one draws the boundary in (a), and a thermodynamically consistent procedure will be described for doing this. The chemical potentials depend sensitively on the stoichiometry of the alloy; the slope of chemical potential versus composition at the stoichiometric composition becomes infinite as T->OK. It is shown for a binary alloy how the chemical potentials can be obtained analytically within a dilute solution approximation, based on calculations of the three basic point defect energies.