Robust quantum-based interatomic potentials for multiscale modeling in transition metals
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First-principles generalized pseudopotential theory (GPT) provides a fundamental basis for transferable multi-ion interatomic potentials in transition metals and alloys within density-functional quantum mechanics. In the central body-centered cubic (bcc) metals, where multi-ion angular forces are important to materials properties, simplified model GPT (MGPT) potentials have been developed based on canonical d bands to allow analytic forms and large-scale atomistic simulations. Robust, advanced-generation MGPT potentials have now been obtained for Ta and Mo and successfully applied to a wide range of structural, thermodynamic, defect, and mechanical properties at both ambient and extreme conditions. Selected applications to multiscale modeling discussed here include dislocation core structure and mobility, atomistically informed dislocation dynamics simulations of plasticity, and thermoelasticity and high-pressure strength modeling. Recent algorithm improvements have provided a more general matrix representation of MGPT beyond canonical bands, allowing improved accuracy and extension to f-electron actinide metals, an order of magnitude increase in computational speed for dynamic simulations, and the development of temperature-dependent potentials.
I. INTRODUCTION
The prospect of modeling across length scales all the way from the atomic to the continuum level to achieve a predictive multiscale description of mechanical properties such as plasticity and strength has attracted widespread research interest in the last decade.1 One of the most fundamental and important problems in such multiscale modeling is that of bridging the gap between firstprinciples quantum mechanics, from which true predictive power for real materials emanates, and the largescale atomistic simulation of thousands or millions of atoms, which is usually essential to describe the complex atomic processes that link to higher length and time scales. For example, to model single-crystal plasticity at micron length scales via dislocation-dynamics (DD) simulations that evolve the detailed dislocation microstructure requires accurate large-scale atomistic information on the mobility and interaction of individual a)
Address all correspondence to this author. e-mail: [email protected] This paper was selected as the Outstanding Meeting Paper for the 2005 MRS Spring Meeting Symposium EE Proceedings, Vol. 882E. DOI: 10.1557/JMR.2006.0070
dislocations. As indicated in Fig. 1, there currently exists a wide spectrum of atomic-scale simulation methods in condensed-matter and materials physics, extending from essentially exact quantum-mechanical techniques to classical descriptions with totally empirical force laws. All of these methods fall into one of two distinct categories, which are separated by a material-dependent gap. On one side of this gap are electronic methods based on direct quantum-mechanical treatments. These include quantum simulations that attempt to treat electron and ion motion on an equal footing, solving quantum-mechanical equations on the
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