title: Gradient equivalent crystal theory.
abstract: This paper presents an extension of the formalism of equivalent crystal theory (ECT) by introducing an electron density gradient term so that the total model density becomes a more accurate representation of the real local density. Specifically, we allow for the electron density around a lattice site to have directionality, in addition to an average value, as assumed in ECT. We propose that an atom senses its neighbouring density as a weighted sum-the weights given by the its own electronic probability. As a benchmark, the method is used to compute vacancy migration energy curves of iron. These energies are in good agreement with previously published results.
authors.affiliation: Department of Physics, Yeshiva University, New York, NY 10033, USA.
authors.forename: F R
authors.initials: FR
authors.lastname: Zypman
authors.forename: J
authors.initials: J
authors.lastname: Ferrante