With the ever growing number of proposed desnity functional theory (DFT) functionals it becomes necessary to thoroughly screen any new method to determine its merit. Especially relevant methods include a proper description of the van der Waals (vdW) interaction, which can prove vital to a correct description of a myriad of systems of technological importance. The first part of this dissertation explores the utility of several vdW-inclusive DFT functionals including optB86b-vdW, optB88-vdW, optPBE-vdW, revPBE-vdW, rPW86-vdW2, and SCAN+rVV10 by applying them to model systems of small organic molecules, pyridine and thiophene, on transition metal surfaces. Overall, we find the optB88-vdW functional gives the best, most balanced description of both thiophene and pyridine on transition metal surfaces while revPBE-vdW, rPW86-vdW2, and SCAN+rVV10 functionals perform especially poorly for these systems. In the second part of this dissertation we change our focus to potential applications of DFT. Specifically, we study the hydrodesulfurization (HDS) process and molecules that could be used in molecular electronics. The removal of sulfur containing molecules from petrochemicals through HDS is an exceptionally important process economically, and the field of molecular electronics is rapidly developing with hopes of competing with and replacing their silicon analogues. First we investigate the hydrodesulfurization of thiophene. In this dissertation we manage to map the HDS rate of thiophene in realistic reaction conditions to the charge transfer and adsorption energy of thiophene on bare transition metal surfaces in hopes of predicting ever more active HDS catalysis. Finally we look at the adsorption of polythiophenes and 5,14-dihydro-5,7,12,14-tetraazapentacene (DHTAP) on Au(111) and Cu(110). We find that polythiophenes may dissociate of Au(111), presenting an issue for their use in molecular electronics. DHTAP, in contrast, proves to a suitable candidate for use practical devices.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Malone, Walter, "A Theoretical Investigation of Small Organic Molecules on Transition Metal Surfaces" (2019). Electronic Theses and Dissertations. 6344.