Gradient equivalent crystal theory

Abstract

This paper presents an extension of the formalism of equivalent crystal theory (ECT) byintroducing an electron density gradient term so that the total model density becomes amore accurate representation of the real local density. Specifically, we allow for the electrondensity around a lattice site to have directionality, in addition to an average value, asassumed in ECT. We propose that an atom senses its neighbouring density asa weighted sum—the weights given by the its own electronic probability. As abenchmark, the method is used to compute vacancy migration energy curves ofiron. These energies are in good agreement with previously published results.