Developing a Virtual Vault for Pseudopotentials: A NNIN/C Initiative

Stewart, Derek. (2010) Developing a Virtual Vault for Pseudopotentials: A NNIN/C Initiative. In: Nanoinformatics 2010, November 3 - 5, 2010, Arlington, VA. (Unpublished)

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Abstract

First principle simulations using approaches like density functional theory have become an important tool in understanding the properties of materials and nanostructures. In some cases, these techniques have even demonstrated powerful predictive capabilities that have led to the discovery of new materials and physical phenomena. Given the widespread use of these approaches, it is important to develop cyberinfrastructure resources that provide trusted calculation components to the scientific community. Density functional simulations based on plane wave pseudopotential approaches provide the dominant approach for computational modeling of materials and nanostructures and several software packages are available at little or no cost. Pseudopotentials provide a computationally efficient way to describe the scattering of electrons from ions in a material. While electron scattering from atoms can be described using the full ion potential, this requires a large plane wave basis set and leads to time consuming calculations that dramatically limit the number of atoms that can be considered in a system. By designing shallower pseudopotentials that require a smaller basis set, yet still provide near identical scattering properties, plane wave pseudopotential codes can simulate much larger scale atomistic systems. However, the design of these pseudopotentials is still something of a black art and researchers spend a great deal of time validating pseudopotentials on standard systems before they can be used with confidence in a research setting. In addition, since different codes have different pseudopotential formats, the transfer of pseudopotentials between codes has been fairly limited. To address these issues, the National Nanotechnology Infrastructure Network Computation Project (NNIN/C) has developed a Virtual Vault for Pseudopotentials. This cyberinfrastructure resource contains a centralized clearinghouse for information related to pseudopotentials (online collections, translators, generators, and references). In addition, we have developed a PHP-SQL database of pseudopotentials that can be accessed online. This database contains over 600 pseudopotential files drawn from several different plane wave codes. Users can interface this data through an online periodic table to find information related to a particular atom. Users can also search the database based on a given element and compare available pseudopotentials based on criteria such as exchange-correlation functional, pseudopotential class (i.e., ultra-soft, norm-conserving), parent electronic structure code, and more. This database provides the first centralized resource for pseudopotentials that spans multiple electronic codes. I will also discuss our current effort to provide metrics of pseudopotentials, including the plane wave cutoff required, predicted lattice constant and bulk modulus. In the near future, users will also have the ability to upload new pseudopotentials for evaluation, list published papers that used the pseudopotential, and also provide comments for proper usage.

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