Kohn-Sham density functional theory (KS-DFT) is one of the most widely used electronic
structure methods. It is used to find the various properties of atoms, molecules, clusters,
and solids. In principle, results for these properties can be found by solving self-consistent
one-electron Schrödinger-like equations based on density functionals for the energy. In
practice, the density functional for the exchange-correlation contribution to the energy
must be approximated. The accuracy of practical DFT depends on the choice of density
functional approximation (DFA) and also on the electron density produced by the DFA.
The SCAN(strongly constrained and appropriately normed) functional developed by Sun,
Ruzsinszky, and Perdew is the first meta-GGA (meta-generalized gradient approximation)
functional that is constrained to obey all 17 known exact constraints that a meta-GGA
can. SCAN has been found to outperform most other functionals when it is applied to
aqueous systems. However, density-driven errors (energy errors occurring from an inexact
density produced by a DFA) hinder SCAN from achieving chemical accuracy in some systems, including water. Density-corrected DFT (DC-DFT) can alleviate this shortcoming
by adopting a more accurate electron density which, in most applications, is the electron
density obtained at the Hartree-Fock level of theory, due to its relatively low computational
cost. In the second chapter, calculations to determine the accuracy of the HF-SCAN functional for water clusters are performed. The interaction and binding energies of water clusters in the BEGDB and WATER27 data sets are computed, and then the spurious charge transfer in deprotonated, protonated, and neutral water dimer is interpreted. The density-corrected SCAN (DC-SCAN) functional elevates the accuracy of SCAN toward the CCSD(T) limit, not only for the neutral water clusters but also for all considered hydrated ion systems (to a lesser extent). In the third chapter, the barrier heights of the BH76 test set are analyzed. Three fully non-local proxy functionals (LC-ωPBE, SCAN50%, and SCAN-FLOSIC) and their selfconsistent proxy densities are used. These functionals share two important points of similarity to the exact functional. They produce reasonably accurate self-consistent barrier
heights and their self-consistent total energies are nearly piecewise linear in fractional electron number. Somewhat-reliable cancellation of density - and functional-driven errors for the energy has been established. / Physics
| Identifer | oai:union.ndltd.org:TEMPLE/oai:scholarshare.temple.edu:20.500.12613/8493 |
| Date | January 2023 |
| Creators | Bhetwal, Pradeep |
| Contributors | Perdew, John P., Perdew, John P., Ruzsinszky, Adrienn, Wu, Xifan, Carnevale, Vincenzo |
| Publisher | Temple University. Libraries |
| Source Sets | Temple University |
| Language | English |
| Detected Language | English |
| Type | Thesis/Dissertation, Text |
| Rights | IN COPYRIGHT- This Rights Statement can be used for an Item that is in copyright. Using this statement implies that the organization making this Item available has determined that the Item is in copyright and either is the rights-holder, has obtained permission from the rights-holder(s) to make their Work(s) available, or makes the Item available under an exception or limitation to copyright (including Fair Use) that entitles it to make the Item available., http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | http://dx.doi.org/10.34944/dspace/8457, Theses and Dissertations |
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