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Hammes-Schiffer, Sharon Makri, Nancy Vura-Weis, Joshua Wagner, Lucas Culpitt, Tanner P. 2020-03-02T22:38:39Z 2020-03-02T22:38:39Z 2022-03-03T10:15:30Z 2019-10-17 2019-12 The nuclear-electronic orbital (NEO) method is a multicomponent approach that allows the quantum mechanical treatment of electrons and specified protons on the same quantum mechanical level. NEO does not make the Born-Oppenheimber approximation between electrons and select protons, and therefore has great potential in applications to non-Born-Oppenheimer processes such as proton-coupled electron transfer (PCET). Additionally, NEO can also capture nuclear quantum effects such as zero-point energy and proton delocalization in a direct and efficient manner. This dissertation describes the development of NEO methods for calculating both ground and excited state molecular properties. For the ground state, a general multicomponent embedding scheme is developed and tested within the NEO framework to obtain nuclear densities. Machinery is also presented for identifying the character and stability of NEO self-consistent field (SCF) solutions, allowing the differentiation between minima and saddle points. For excited states, the linear response multicomponent time-dependent density functional theory (TDDFT) is derived and implemented within the NEO framework. The results for nuclear vibrational excitations of interest corresponding to single or multiple protons calculated with NEO-TDDFT are accurate when the method is used in conjunction with large nuclear and electronic basis sets. Lastly, a scheme is presented for coupling proton vibrational excitation energies calculated with NEO-TDDFT to the normal modes associated with the other nuclei. This scheme, denoted NEO-DFT(V), thereby allows for full molecular vibrational frequencies to be calculated. These NEO methods provide the foundation for a wide range of applications, especially those involving non-Born-Oppenheimber processes or nuclear quantum effects. Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-12-01 The student, Tanner Culpitt, accepted the attached license on 2019-10-16 at 10:14. The student, Tanner Culpitt, submitted this Dissertation for approval on 2019-10-16 at 10:14. This Dissertation was approved for publication on 2019-10-17 at 15:11. DSpace SAF Submission Ingestion Package generated from Vireo submission #14498 on 2020-02-28 at 17:35:40 Made available in DSpace on 2020-03-02T22:38:39Z (GMT). No. of bitstreams: 2 CULPITT-DISSERTATION-2019.pdf: 37016481 bytes, checksum: 62616a58c8e1890359d849f94503444b (MD5) LICENSE.txt: 4211 bytes, checksum: c22bca9b1e851982122e955bd9b584dc (MD5) Previous issue date: 2019-10-17 Embargo set by: Seth Robbins for item 113977 Lift date: 2022-03-02T22:39:04Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system Limited Restriction Lifted for Item 113977 on 2022-03-03T10:15:30Z. application/pdf http://hdl.handle.net/2142/106433 en Copyright 2019 Tanner Culpitt electronic structure non-Born-Oppenheimer DFT TDDFT Wave Function Development of non-born-Oppenheimer methods for ground and excited state molecular properties text text Chemistry Chemistry University of Illinois at Urbana-Champaign Dissertation Ph.D.