Look at literature if somebody has compared

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Look at literature if somebody has compared functionals for systems similar to yours! Increasing quality and computational cost
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its.unc.edu 56 Percentage of occurrences of the names of the several functionals indicated in Table 2, in journal titles and abstracts, analyzed from the ISI Web of Science (2007). S.F. Sousa, P.A. Fernandes and M.J. Ramos, J . Phys. Chem. A 10.1021/jp0734474 S1089-5639(07)03447-0 Density Functionals Density Functionals
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its.unc.edu 57 Problems with DFT Problems with DFT ground-state theory only universal functional still unknown even hydrogen atom a problem: self-interaction correction no systematic way to improve approximations like LDA, GGA, etc. extension to excited states, spin multiplets, etc., though proven exact in theory, is not trivial in implementation and still far from being generally accessible thus far
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its.unc.edu 58 DFT Developments DFT Developments Theoretical Extensions to excited states, etc. Better functionals (mega-GGA), etc Understanding functional properties, etc. Conceptual More concepts proposed, like electrophilicity, philicity, spin- philicity, surfaced-integrated Fukui fnc Dynamic behaviors, profiles, etc. Computational Linear scaling methods QM/MM related issues Applications
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its.unc.edu 59 Examples DFT vs. HF Examples DFT vs. HF Hydrogen molecules - using the LSDA (LDA)
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its.unc.edu 60 Chemical Reactivity Theory Chemical Reactivity Theory Chemical reactivity theory quantifies the reactive propensity of isolated species through the introduction of a set of reactivity indices or descriptors. Its roots go deep into the history of chemistry, as far back as the introduction of such fundamental concepts as acid, base, Lewis acid, Lewis base, etc. It pervades almost all of chemistry. Molecular Orbital Theory Fukui’s Frontier Orbital (HOMO/LUMO) model Woodward-Hoffman rules Well developed: Nobel prize in Chemistry, 1981 Problem: conceptual simplicity disappears as computational accuracy increases because it’s based on the molecular orbital description Density Functional Theory (DFT) Conceptual DFT, also called Chemical DFT, DF Reactivity Theory Proposed by Robert G. Parr of UNC-CH, 1980s Still in development -- Morrel H. Cohen, and Adam Wasserman, J. Phys. Chem. A 2007 , 111,2229
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its.unc.edu 61 DFT Reactivity Theory DFT Reactivity Theory General Consideration E E [N, (r)] E [ ] Taylor Expansion: Perturbation resulted from an external attacking agent leading to changes in N and (r), N and  (r),  ' ' 2 ! , , 2 2 2 2 r r r r r r r r 2 1 r r r r r r 2 d d E d N E N N N E d E N N E N E N N E E N N N       Assumptions: existence and well-behavior of all above partial/functional derivatives
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its.unc.edu 62 Conceptual DFT Conceptual DFT Basic assumptions E E [N, (r)] E [ ] Chemical processes, responses, and changes expressible via Taylor expansion Existence, continuous, and well- behavedness of the partial derivatives
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its.unc.edu 63 DFT Reactivity Indices DFT Reactivity Indices
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