Abstract
We develop an extended cluster expansion (CE) technique, continuous-spin basis variable-lattice cluster expansion (CS-VLCE), enabling complete description of strain effects on alloy configurational energetics for single as well as multiple lattices. In the proposed CS-VLCE, spin variable ω on a virtual lattice is introduced, which specifies the strain of a given cell from the base cell. Basis functions constructed from ωs and those used in the CE satisfy completeness and orthonormality for any atomic arrangement in any strained cell. As an example, combination of the CS-VLCE with first-principles calculation is applied to estimate superlattice formation energy along the [001] direction for Cu-Au binary alloys. We successfully demonstrate that the CS-VLCE can accurately handle strain effects on total energy, which cannot be achieved by the current CE.
