This article shows that, although Boys localization is usually applied to single-electron orbitals, the Boys method itself can be applied to many electron molecular states. For the two-state charge-transfer problem, we show analytically that Boys localization yields the same charge-localized diabatic states as those found by generalized Mulliken–Hush theory. We suggest that for future work in electron transfer, where systems have more than two charge centers, one may benefit by using a variant of Boys localization to construct diabatic potential energy surfaces and extract electronic coupling matrix elements. We discuss two chemical examples of Boys localization and propose a generalization of the Boys algorithm for creating diabatic states with localized spin density that should be useful for Dexter triplet-triplet energy transfer.
Constructing diabatic states from adiabatic states: Extending generalized Mulliken--Hush to multiple charge centers with Boys localization. Joseph E. Subotnik, Sina Yeganeh, Robert J. Cave, and Mark A. Ratner, J. Chem. Phys. 129, 244101 (2008), DOI:10.1063/1.3042233.