This award supports research and education in developing and improving methods for predicting the electronic and geometrical structure of both bulk materials and molecular complexes. Research extends Density functional theory (DFT) which has been a successful method for much of such matter. The primary extension improves the treatment of electron correlations at a distance which lead to the van der Waals interaction. This enhancement expands the use of DFT beyond dense condensed matter and isolated molecules, which can already be treated accurately, and provides capabilities for improved treatment of sparse matter, including biological matter, as well as van der Waals molecular complexes. The research expands on previous enhancements embodied in the non-empirical van der Waals density functional developed by this principal investigator and others. The work being undertaken widens the applicability of the van der Waals density functional to a broad range of system types, and increases its accuracy. Key applications will be addressed in the course of the research that cannot be handled by other methods and which demonstrate the efficacy of the enhancements. The result of this development will include a robust computer codes to be distributed, thus putting the method within easy access of the greater community. The goal of the work is to increase our limited understanding on how the van der Waals interaction merges with the short-range phenomena associated with density overlap, especially in systems too large to be feasibly treated with wave-function methods. Accordingly this allows treatment of of much larger systems than possible at present and increases our understanding of how certain large systems function.
The effort undertaken has broader impacts with both scientific and educational consequences. Though the computational effectiveness of Density Functional Theory has already had a broad impact on materials science and engineering, the work proposed here will extend the usefulness of DFT to a wide range of previously impossible systems which are prevalent and important in many different fields. Early examples include the first calculation from first principles that predicts the twist of DNA. There will be capabilities added that will help with complex materials of the sort needed to study the the hydrogen storage problem for the possible future hydrogen fueled vehicles. Included in the plans are a study of molecular configurations that are relevant to understanding drug action and drug design. This work is shared widely in the scientific literature and conferences and the computer codes developed are shared.
NONTECHNICAL SUMMARY: This award supports research and education in developing and improving methods for predicting the electronic and geometrical structure of both bulk matter and individual molecules. Research extends Density functional theory which has been a successful method for many types of materials. The primary extension improves the treatment of forces between molecules that are separated by modest to large distances. This enhancement provides capabilities for improved treatment of sparse matter, including biological matter, as well as weak molecular complexes. The work being undertaken widens the applicability of the theoretical and computational methods and increases accuracy. Key applications will be addressed in the course of the research that cannot be handled by other methods and which demonstrate the efficacy of the enhancements. The result of this development will include a robust computer codes to be distributed, thus putting the method within easy access of the greater community. This allows treatment of of much larger systems than possible at present and increases our understanding of how certain large systems function.
The effort undertaken has broader impacts with both scientific and educational consequences. Though the computational effectiveness of Density Functional Theory has already had a broad impact on materials science and engineering, the work proposed here will extend the usefulness of the theory to a wide range of previously impossible systems which are prevalent and important in many different fields. Early examples include the first calculation that predicts the twist of DNA. There will be capabilities added that will help with complex materials of the sort needed to study the the hydrogen storage problem for the possible future hydrogen fueled vehicles. Included in the plans are a study of molecular configurations that are relevant to understanding drug action and drug design. This work is shared widely in the scientific literature and conferences and the computer programs are made freely available.
The most common chemical bonds in nature are the covalent and ionic bonds that hold together most hard materials, including metals, minerals, and semiconductors. More difficult to describe theoretically are the weak "van der Waals" bonds that are responsible for the cohesion in various specialized types of materials, such as organic crystals, and which also play an important role in biology and in problems such as hydrogen storage in the energy industry. The goals of this project have been to develop improved theoretical and computational methods for modeling these van der Waals interactions, and to apply these methods to understand and characterize the bonding in materials of importance for biological and energy applications. During the course of this project, we developed a new and improved version of a technique for modeling the van der Waals interaction, which we denoted as vdW-DF2. Tests carried out as part of this project showed that vdW-DF2 gives improved predictions of the structural geometries and bonding properties for a "test set" of molecules for which the vdW interactions are already well characterized, and gave excellent agreement with experiment in some test situations in which the experiments are complete enough to allow a detailed characterization of the vdW bonding. Numerous applications of the vdW-DF2 description (and of vdW-DF, a less accurate version developed under a previous NSF grant) were carried out under this project. These included: a study of the interactions of DNA base pairs, providing an improved understanding of the DNA double-helix structure; the adsorption of molecules such as water (H2O), hydrogen (H2), and butane (C4H10) on metal surfaces; adsorption of organic molecules on surfaces of oxides such as MgO; and the behavior of hydrogen transfer reactions in an organic ferroelectric crystal. The project contributed to the understanding and potential utility of several classes of materials that may lead to technologically important applications. The computer codes that were developed under this project, implementing the vdW-DF2 description, were also posted and freely distributed worldwide for open use by the computational materials community. Thus, the project has contributed an important tool that can now be used by other researchers in diverse fields ranging from catalysis, liquid crystals, biological adhesion, and colloidal aggregation phenomena. Finally, the project also contributed to the training and career development of several postdocs and students associated with the project.
