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Abstract:

Although density functional theory (DFT) remains the method of choice for its balance of speed and accuracy in computational screening, semi-local approximations in density functional theory (DFT), such as the generalized gradient approximation (GGA), suffer from many electron self-interaction errors that causes them to predict erroneous spin states and geometries, barrier heights and dissociation energies, and orbital energies, to name a few. I will outline our recent efforts to both understand and correct these errors with a focus on predictive modeling of transition metal chemistry : i) I will describe how DFT+U can be understood as an approach to recover the derivative discontinuity, ii) I will describe how DFT+U affects the density properties of transition metal complexes and surface properties of correlated solids with respect to exact references, iii) I will discuss how to recover the flat-plane condition that is a union of the requirement of piecewise linearity with electron removal or addition as well as unchanged energy when changing the spin of an electron in isoenergetic orbitals. I will show how our built-from-scratch judiciously-modified DFT (jmDFT) functionals can oppose errors inherent in semi-local functionals in a way that is connected to but diverges from hybrid functionals and standard DFT+U. By examining these forms, we can understand why both DFT+U and hybrids commonly increase static correlation errors when improving delocalization errors. We also present fundamental expressions for determining these parameters, mitigating empiricism in jmDFT and DFT+U methods.

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