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Local Volume Effects in the Generalized Pseudopotential Theory
The generalized pseudopotential theory (GPT) is a powerful method for
deriving real-space transferable interatomic potentials. Using a coarse-grained
electronic structure, one can explicitly calculate the pair ion-ion and
multi-ion interactions in simple and transition metals. Whilst successful in
determining bulk properties, in central force metals the GPT fails to describe
crystal defects for which there is a significant local volume change. A
previous paper [PhysRevLett.66.3036 (1991)] found that by allowing the GPT
total energy to depend upon some spatially-averaged local electron density, the
energetics of vacancies and surfaces could be calculated within experimental
ranges. In this paper, we develop the formalism further by explicitly
calculating the forces and stress tensor associated with this total energy. We
call this scheme the adaptive GPT (aGPT) and it is capable of both molecular
dynamics and molecular statics. We apply the aGPT to vacancy formation and
divacancy binding in hcp Mg and also calculate the local electron density
corrections to the bulk elastic constants and phonon dispersion for which there
is refinement over the baseline GPT treatment.Comment: 11 pages, 6 figure
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