DFT calculations of magnetic shielding and quadrupolar coupling in ordered systems: methods and applications to NMR crystallography
| Author(s) | Holmes, Sean | |
| Date Accessioned | 2017-04-25T11:18:13Z | |
| Date Available | 2017-04-25T11:18:13Z | |
| Publication Date | 2017 | |
| Abstract | This dissertation presents quantum-mechanical calculations of nuclear magnetic resonance (NMR) parameters in crystalline solids. Several themes run through the dissertation; they all relate to aspects of the prediction of magnetic-shielding tensors and quadrupolar-coupling tensors for various light nuclides such as 13C, 15N, 17O, 19F, 29Si, 31P, 35Cl, and 43Ca. ☐ A cluster-based computational protocol for modeling NMR parameters in molecular solids, referred to as the symmetry-adapted cluster ansatz, is discussed. This approach uses a shell of molecules to represent the local lattice environment by judiciously selecting molecules to maintain the rotational symmetry elements of the crystal space group. Chapter 2 illustrates the utility of the cluster-based approach through calculations of the principal components of the 13C magnetic-shielding tensors of 155 carbon sites. In Chapter 3, this analysis is applied to the assignment of the 13C chemical-shift tensors of the aromatic compound indigo. Chapter 4 focuses on comparison of 13C, 15N, 19F, and 31P magnetic-shielding tensors calculated using the cluster ansatz with results of using the periodic GIPAW approach. This analysis is based on calculation of the magnetic-shielding tensors of 131 NMR-active sites in 72 materials. Furthermore, benchmark calculations are provided for a large number of density functionals, including GGA, meta-GGA, and hybrid approaches. ☐ Chapters 5 and 6 expand the focus to the calculation of NMR parameters in network solids. Chapter 5 presents 43Ca magnetic-shielding and quadrupolar-coupling tensors in calcium carboxylates, and Chapter 6 presents 29Si and 31P magnetic-shielding tensors in covalent network solids. In both chapters, the cluster-based approach is benchmarked against the GIPAW approach, and various model chemistries are assessed. The calculation of 29Si and 31P magnetic-shielding tensors employs an approach in which the outermost atoms of the cluster are replaced with pseudoatoms that reduce the overall charge on the cluster to permit SCF convergence. ☐ In addition to benchmarking cluster-based calculations of solid-state NMR parameters, applications in NMR crystallography, based on computed 17O quadrupolar-coupling tensors, are assessed. In particular, a method of semi-empirical geometry optimization is proposed, in which a dispersion force field is parameterized to produce structures that yield accurate predictions of 17O quadrupolar-coupling tensors. | en_US |
| Advisor | Dybowski, Cecil | |
| Degree | Ph.D. | |
| Department | University of Delaware, Department of Chemistry and Biochemistry | |
| Unique Identifier | 983833820 | |
| URL | http://udspace.udel.edu/handle/19716/21253 | |
| Publisher | University of Delaware | en_US |
| URI | https://search.proquest.com/docview/1884605826?accountid=10457 | |
| Title | DFT calculations of magnetic shielding and quadrupolar coupling in ordered systems: methods and applications to NMR crystallography | en_US |
| Type | Thesis | en_US |