Browsing by Author "Graham, Daniel"
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Item Absolutely Localized Huzinaga Projection Based Embedding for Efficient and Accurate Molecular Modeling(2022-05) Graham, DanielWithin computational chemistry, Kohn-Sham density functional theory has become invaluable for low computational cost quantum mechanical calculations.However, computationally expensive post-Hartree-Fock wave function quantum methods are still required to accurately model many chemical systems. We are able to recreate post-Hartree-Fock wave function levels of computational accuracy while only incurring computational costs on par with density functional theory using our absolutely localized Huzinaga level-shift projection based wave function in density functional theory embedding method. Computationally accurate gas adsorption energies on transition metal clusters of metal organic frameworks, spin transition energies of iron models, full configuration interaction (FCI) level energies of small molecules on surfaces and analytical nuclear gradients of our embedding method have been developed and are reported here. We have demonstrated many valuable features of our embedding method such as systematic improvability, applicability to a breadth of chemical problems, and low computational cost for highly accurate calculations. Our Huzinaga embedding method pushes the boundaries of computational chemistry by enabling the calculation of accurate molecular energies for chemical systems previously beyond the scope of existing computational methods. We anticipate our method will be of interest to anyone studying large, complex systems that cannot be accurately modeled using density functional theory and are too large for traditional post-Hartree-Fock methods.Item Agglomeration, Accessibility, and Productivity: Evidence for Large Urbanized Areas in the US.(2016) Melo, Patricia; Graham, Daniel; Levinson, David M; Aarabi, SarahThis paper undertakes an empirical analysis with the aim of improving the current understanding of the relationship between labor productivity and urban agglomeration economies across a sample of urbanized areas in the US. Agglomeration economies are represented with driving time measures of employment accessibility to establish a direct account for the link between transport and agglomeration economies. The paper investigates the presence of nonlinearities in the relationship between labor productivity and agglomeration economies, and examines the spatial decay pattern of the effects arising from this relationship. The findings indicate that there is considerable nonlinearity in the relation between productivity and transport induced agglomeration effects, implying that the estimation of country-level aggregate elasticities is likely to misrepresent the actual magnitude of any productivity gains from urban agglomeration. The results also suggest that the magnitude of the productivity-agglomeration effects decays very rapidly with time and is very strong within 20 minutes driving time. This suggests that knowledge spillover externalities are likely to be a very important Marshallian source of agglomeration economies.Item Data for "Robust, accurate, and efficient: quantum embedding using the Huzinaga level-shift projection operator for complex systems"(2019-11-27) Graham, Daniel; Wen, Xuelan; Chulhai, Dhabih; Goodpaster, Jason; jgoodpas@umn.edu; Goodpaster, Jason; University of Minnesota Chemistry Department Goodpaster LabAll output and relevant molden orbital files for ground state Huzinaga embedding WF-in-DFT energy calculations.