Poster #P40




Adaptive Hybrid Density Functionas

Danish Khan, Alastair J. A. Price, Maximilian L. Ach, O. Anatole von Lilienfeld



Exact exchange and correlation contributions are known to crucially affect electronic states, which in turn govern covalent bond formation and breaking in chemical species. Empirically averaging the exact exchange admixture and the amount of correlation over configurational and compositional degrees of freedom, hybrid density functional approximations (DFAs) have been widely successful, yet have fallen short to reach explicitly correlated high level quan- tum chemistry accuracy in general. Using quantum machine learning, we have adaptified hybrid DFAs by generating optimal admixture ratios of ex- act exchange or of correlation “on the fly”, specifically for any chemical com- pound. Adaptive exchange in the PBE0 hybrid DFA yields atomization ener- gies sufficiently accurate to effectively cure the infamous spin gap problem in DFT, and also improves electron densities, and HOMO-LUMO gaps in organic molecules. Using adaptive PBE0, we revised the entire QM9 data set present- ing more accurate quantum properties that include, on average, stronger cova- lent binding, larger band-gaps, more localized electron densities, and slightly larger dipole-moments. Adaptive PBE correlation (in conjunction with 100% HF exchange) also affords much improved atomization energies, and even en- ables covalent bond dissociation.






 

  •   University of Toronto