eprintid: 33801 rev_number: 31 userid: 6157 dir: disk0/00/03/38/01 datestamp: 2018-06-15 14:50:12 lastmod: 2018-07-30 16:53:26 status_changed: 2018-06-15 14:50:12 type: thesis_degree metadata_visibility: show contact_email: erb74@pitt.edu item_issues_id: duplicate_title_34293 item_issues_type: duplicate_title item_issues_description: Duplicate title to Berquist, Eric Decomposition of Intermolecular Interactions in Ab Initio Spectroscopy. Doctoral Dissertation, University of Pittsburgh. (Unpublished) item_issues_timestamp: 2018-04-14 06:02:13 item_issues_status: autoresolved item_issues_count: 0 eprint_status: archive creators_name: Berquist, Eric creators_email: erb74@pitt.edu creators_id: erb74 creators_orcid: 0000-0001-8186-9522 title: Decomposition of Intermolecular Interactions in Ab Initio Spectroscopy ispublished: unpub divisions: sch_as_chemistry full_text_status: public keywords: ionic liquids, carbon dioxide, infrared spectroscopy, energy decomposition analysis, absolutely localized molecular orbitals, polarizability, linear response abstract: Spectroscopy, the molecular response to electromagnetic radiation of different wavelengths, is one of the most powerful experimental tools for interrogating a molecule's structure and dynamics as it interacts with its environment. However, relating a spectroscopic signature to a molecular picture relies on sophisticated computational approaches, which offer a wealth of methods for identifying structures, intermolecular interactions, and their correlation with spectroscopic response. This thesis focuses on the how to correlate a molecule's structure and interactions with its environment via ab initio calculation of spectroscopic parameters. To build a molecular picture of carbon dioxide dynamics in ionic liquids (ILs), quantum chemical calculations on small clusters qualitatively reproduced the experimental ordering for carbon dioxide's asymmetric vibrational stretch peak position which shifts when dissolved in a series of ILs with varying anions. To uncover the physical origin of the shift, the language of decomposition analysis based on absolutely localized molecular orbitals (ALMO-EDA) was translated from energies to vibrational frequencies. Geometric distortion of carbon dioxide, as a result of charge transfer (CT) from the anion into the carbon dioxide, is the driving force for differentiating the carbon dioxide asymmetric stretch shift in different IL anions. After validating these simple models, we further decomposed the CT contribution into geometry and curvature mechanisms, finding that CT is a significant contributor in both the geometry optimization and frequency calculation steps. A comparison between ALMO-EDA and symmetry-adapted perturbation theory (SAPT) showed that while dispersion dominates the binding energy, excellent correlation between both total interaction energies and individual components for ALMO-EDA and SAPT validates the use of DFT, enabling the construction of a semiempirical spectroscopic map. This decomposition presented the first application of an EDA outside the energy realm into molecular properties; however, it is not generally applicable to arbitrary perturbations. A reformulation of the canonical linear response equations for use with ALMOs provides a direct connection between EDA terms and their corresponding contribution to spectra. Results for argon-lithium cation dimer polarizabilities show that allowing CT is equally important in both the underlying ground-state wavefunction and the response calculation, and should not be confused with basis set superposition error. date: 2018-06-15 date_type: published pages: 288 institution: University of Pittsburgh refereed: TRUE related_url_url: https://github.com/berquist/dissertation related_url_desc: GitHub repository containing full working LaTeX source and other notes etdcommittee_type: committee_chair etdcommittee_type: committee_member etdcommittee_type: committee_member etdcommittee_type: committee_member etdcommittee_name: Lambrecht, Daniel etdcommittee_name: Jordan, Kenneth etdcommittee_name: Garrett-Roe, Sean etdcommittee_name: Yaron, David etdcommittee_email: qclab@pitt.edu etdcommittee_email: jordan@pitt.edu etdcommittee_email: sgr@pitt.edu etdcommittee_email: yaron@cmu.edu etdcommittee_id: qclab etdcommittee_id: jordan etdcommittee_id: sgr etdcommittee_orcid: 0000-0001-5326-0234 etdcommittee_orcid: 0000-0001-6199-8773 etdcommittee_orcid: 0000-0001-8186-9522 etd_defense_date: 2018-03-23 etd_approval_date: 2018-06-15 etd_submission_date: 2018-02-20 etd_release_date: 2018-06-15 etd_access_restriction: immediate etd_patent_pending: FALSE thesis_type: dissertation degree: PhD citation: Berquist, Eric (2018) Decomposition of Intermolecular Interactions in Ab Initio Spectroscopy. Doctoral Dissertation, University of Pittsburgh. (Unpublished) document_url: http://d-scholarship-dev.library.pitt.edu/33801/1/eric_john_berquist_etd.pdf document_url: http://d-scholarship-dev.library.pitt.edu/33801/7/eric_john_berquist_etd.pdf