자료유형  

 학위논문

Control Number  

0017161133

International Standard Book Number  

9798382835419

Dewey Decimal Classification Number  

540

Main Entry-Personal Name  

Chen, Junhan.

Publication, Distribution, etc. (Imprint  

[S.l.] : University of Pennsylvania., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

178 p.

General Note  

Source: Dissertations Abstracts International, Volume: 85-12, Section: B.

General Note  

Advisor: Subotnik, Joseph E.

Dissertation Note  

Thesis (Ph.D.)--University of Pennsylvania, 2024.

Summary, Etc.  

요약Molecular dynamics at metal interfaces is a critical research area that underlies significant chemical processes involved in technology, energy and medical applications. The Born-Oppenheimer approximation, which is the fundamental theoretical approximation underlying almost all ab initio molecular dynamics approaches, often breaks down at interfaces, because charge transfer occurs and nuclei move along multiple potential energy surfaces. The presence of such complicated curve crossings requires that a meaningful theoretical description must involve not just one unique ground state, but also one or more relevant excited states. Obtaining such states becomes extremely hard near metal surfaces, as hard as picking a needle in a haystack, because there is a continuum of electronic states present at metal surfaces: how should we pick the relevant electronic states (assuming many states are irrelevant)? In this thesis, we develop several electronic structure methods for solving such a problem, using the Anderson impurity model as a test case. On the one hand, to test our methodologies, we quantitatively benchmark our results for ground state properties against numerical exact results from numerical renormalization group (NRG) theory. On the other hand, to learn about new physical processes, we qualitatively assess the predicted excited state properties, especially curve crossing trends. As far as methods are concerned, we first investigate a selective configuration interaction approach; here, ground state results match with NRG results across a wide range of parameters, but we find this approach is not easy to extrapolate to realistic systems. Second, we investigate a multireference Hartree-Fock wave function, with both open-shell and closed-shell characters; here, again, we find strong ground state results and show that effectively an active space can be isolated, but we find that the algorithm in some ways does not include enough electronic relaxation. Third, we design a new complete active space approach based on a novel constraint appropriate to interfaces. This last approach appears to be the very best of all choices so far and can generate both accurate ground state wave function as well as excited states, all with smooth transitions. Using the latter approach, future development of gradients and non-adiabatic couplings should allow for the study of non-adiabatic dynamics for molecules near metal surfaces.

Subject Added Entry-Topical Term  

Chemistry.

Subject Added Entry-Topical Term  

Physical chemistry.

Subject Added Entry-Topical Term  

Computational chemistry.

Subject Added Entry-Topical Term  

Molecular chemistry.

Index Term-Uncontrolled  

Molecular dynamics

Index Term-Uncontrolled  

Anderson impurity model

Index Term-Uncontrolled  

Numerical renormalization group theory

Index Term-Uncontrolled  

Born-Oppenheimer approximation

Index Term-Uncontrolled  

Hartree-Fock wave function

Added Entry-Corporate Name  

University of Pennsylvania Chemistry

Host Item Entry  

Dissertations Abstracts International. 85-12B.

Electronic Location and Access  

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Control Number  

joongbu:654491