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CC BY V4.0, Open Access
Dissertation
Modeling the Quantum Behavior of Hydrogen using Density Functional Theory, Quantum Monte Carlo, and Machine Learning
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000005465
Handle:
https://hdl.handle.net/2376/118896
Abstract
Computation and simulation play a central role in physics. As applied to atoms, molecules, and condensed-matter systems, this is based on quantum mechanics. Many calculations are only possible though due to approximations made. Two of particular interest in this dissertation are the consideration of static and classical ions (nuclei) and the use of pseudopotentials to replace the divergent Coulomb interaction between ions and electrons. For many systems, these approximately work or are expected to work well. There are others though where things are less clear. Dense hydrogen is one such system, and one that is both rich in physics and has the potential for significant practical applications.
In this dissertation, the aforementioned approximations as made in perhaps the most-used computational method, density-functional theory, and as applied to dense hydrogen are investigated. This includes the effect of the pseudopotential approximation on the phase diagram and superconductivity of solid hydrogen and also the nuclear quantum states of molecular hydrogen adsorbed to a surface. For the latter, quantum Monte Carlo is used in a novel way that supplements density-functional theory. As a supplemental study, a reduction of the computational cost of density-functional theory, from $O(N^3_e)$ to $O(N_e)$ where $N_e$ is the number of electrons, is considered using machine learning. Altogether, these results are expected to be significant for computational physics, the field of dense hydrogen, and other fields such as
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Details
- Title
- Modeling the Quantum Behavior of Hydrogen using Density Functional Theory, Quantum Monte Carlo, and Machine Learning
- Creators
- Jeevake Attapattu
- Contributors
- Jeffrey M McMahon (Advisor)Michael Forbes (Committee Member)Jacob Leachman (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Physics and Astronomy
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 148
- Identifiers
- 99900592257101842
- Language
- English
- Resource Type
- Dissertation