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Improvements in Density Functional Theory Calculations, Analysis, and Applications

  • Author(s): Veccham Krishna Prasad, Srimukh Prasad
  • Advisor(s): Head-Gordon, Martin P.
  • et al.
Abstract

Density functional theory (DFT) is the most widely used quantum chemistry method. This dissertation explores and advances different aspects of DFT. The computational cost of DFT scales as the third power of the system size. In Chapter 2, we introduce an embedded many-body expansion, called the polarized many-body expansion, which removes the computational bottleneck steps in DFT calculations by exploiting the pairwise additivity of some components of interaction energy in molecular clusters. Energy decomposition analysis fragments interaction energy into physico-chemically meaningful components like permanent electrostatics, dispersion, polarization, and charge transfer. In Chapter 3, we introduce a non-perturbative approach to decompose charge transfer energy into pairwise additive terms. This approach improves upon the previous perturbative approach and can be applied to chemical complexes with both weak and strong charge transfer interactions. Different density functional approximations (DFAs) show varied performance for predicting properties of different chemical systems. In Chapters 4 and 5, we identify DFAs which give good accuracy for predicting the interaction energy of hydrogen with different model binding sites. These DFAs can potentially be used for in silico high-throughput screening of materials capable of storing hydrogen at desired conditions.

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