Our recent "B13" exact-exchange-based and strongly-correlated density functional [J. Chem. Phys. 138, 074109 (2013)] admits fractional occupancies as occur in multi-reference pure states. Our latest investigations on the potential-energy ground and excited-state surfaces of ethylene will be discussed. There is much to be learned about B13, and other density functionals, from this challenging problem involving singlet-singlet crossings, singlet-triplet crossings, avoided crossings, etc...

B13 strongly-correlated density functional and multi-reference states

251st National Meeting (2016)

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