Local Volume Effects on Defects and Free Surfaces

Abstract

Abstract In this chapter, we transform the total-energy functional for elemental metals, as given by generalized pseudopotential theory (GPT), from a bulk representation based on the global atomic volume to an electron-density representation based on the local valence electron density. This local electron density (LED) representation of the GPT allows one to treat surface energies directly, as well as important local volume effects on defect energies in nontransition metals. Also possible in the case of transition metals is an alternate hybrid method, which retains the LED framework for non-d electrons, but for the d electrons joins the model-GPT with a compatible local density-of-states representation of the d-state energy contributions. This hybrid method is able to treat surface relaxation and reconstruction in central transition metals. Recently, a refined and extended LED version of GPT permits a first-principles calculation of forces and stresses for nontransition metals, in what is now called the adaptive GPT or aGPT. This advance allows fully relaxed defect and surface calculations, as well as dynamic aGPT molecular dynamics simulations.