EAGER: Rung-Reduced Density Functionals for Cost-Capped Ab Initio Molecular Dynamics

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NONTECHNICAL SUMMARYThe project involves the development of new exchange correlation potentials that are computationally cheap and would enable ab initio molecular dynamics on larger systems. This unconventional, promising, but risky approach to developing these correlation potentials qualifies the project for EAGER. Context is the growing importance of ab initio molecular dynamics simulations for predictive simulation of novel material properties. This gives detailed insight into atomic-scale processes that affect bulk properties, even for experimentally inaccessible conditions. The PI's constraint-based (not fitted to data bases) functionals reduce molecular binding energy errors by a factor of two compared to the most popular methods with vibration frequencies, ionization potentials, etc. An enticing and highly unusual route to be explored in this proposal is provided by a recent major advance based on the first fully non-empirical orbital-free kinetic energy functional at the GGA rung. There are four areas of broader impact. Success will transform ab initio molecular dynamics simulations of complicated, challenging materials, particularly on department and group-level machines by keeping standard Kohn-Sham cost-scaling as low as possible. Certain fundamental aspects of pure Density Functional Theory itself (beyond simulations) will be substantially clarified, including spacing of the Jacobs' ladder rungs. International science will be enhanced by involvement with collaborators and their student in Mexico. The postdoctoral scholar will benefit from a high-level academic apprenticeship.TECHNICAL SUMMARYThe project involves the development of new exchange correlation potentials that are computationally cheap and would enable ab initio MD on larger systems. The proposed solution is to approximate exchange-correlation density functionals dependent only on the electron number density and its spatial derivatives, and not explicitly on the Kohn-Sham orbitals. This unconventional, promising, but risky approach qualifies the project for EAGER. Context is the growing importance of ab initio molecular dynamics simulations for predictive simulation of novel material properties. This gives detailed insight into atomic-scale processes that affect bulk properties, even for experimentally inaccessible conditions. The PI's constraint-based (not fitted to data bases) functionals reduce molecular binding energy errors by a factor of two compared to the most popular methods with vibration frequencies, ionization potentials, etc. This "rung reduction" strategy will remove the orbitals from meta-generalized gradient approximation (meta-GGA) functionals to get highly refined GGA functionals. An enticing and highly unusual route to be explored in this proposal is provided by a recent major advance based on the first fully non-empirical orbital-free kinetic energy functional at the GGA rung. There are four areas of broader impact. Success will transform ab initio molecular dynamics simulations of complicated, challenging materials, particularly on department and group-level machines by keeping standard Kohn-Sham cost-scaling as low as possible. Certain fundamental aspects of pure DFT itself (beyond simulations) will be substantially clarified, including spacing of the Jacobs' ladder rungs. International science will be enhanced by involvement with collaborators and their student in Mexico. The postdoctoral scholar will benefit from a high-level academic apprenticeship.