A localized-basis scheme for molecular dynamics

Publisher Website
Google Scholar
Abstract
The combination of molecular dynamics and density-functional theory introduced by Car and Parrinello (CP) has broadened very markedly the range of systems and properties that can be treated on a first-principles basis. The CP formulation involves plane-wave expansions for wavefunctions and potentials and is best suited when the atoms can be represented by weak pseudopotentials. An alternative approach employs expansions in localized orbitals and may prove advantageous where strong potentials are encountered. The approach derives forces from a density functional closely related to the Kohn-Sham functional but defined rigorously on function space, in particular for a sum of site densities. This simplifies force calculation substantially. The site densities are represented via a density basis and the orbitals by an orbital basis of exponentially localized Lambda -functions whose exponents are optimized dynamically. The potential of the approach is demonstrated via explicit calculations, including molecular-dynamics simulations for hydrogen clusters.