Forces and Geometry Optimization in First-Principles Atomic Cluster Calculations

Abstract

ABSTRACTWe make use of the existing formalism for calculating atomic forces within the local density approximation (LDA) to determine forces in all-electron, local orbital electronic structure calculations. The forces are calculated as the proper total energy derivatives, including the necessary basis-set corrections. Our technique evaluates the LDA potential exactly on a variationally determined integration mesh which allows all integrals relevant to the electronic structure problem to be computed to any desired accuracy. We demonstrate the high accuracy of forces calculated using our method with an application to the molybdenum dimer. Several issues concerning the accuracy of the forces are discussed, including self-consistency effects, and the effects of integration error. We discuss the use of the forces in dynamical routines for geometry optimizations.