Organic molecular crystal structure prediction has advanced significantly in recent years, thanks in large part to dispersion-corrected density functional theory (DFT). However, commonly-used generalized gradient approximation (GGA) and hybrid density functionals sometimes perform poorly for crystal structure prediction of conformationally flexible molecules. The problem frequently stems from delocalization error in the approximate density functionals and its impact on conformational energies. This talk will present examples of this behavior in organic and pharmaceutical crystals, and it will discuss various strategies one might employ to address this problem in crystal structure prediction protocols. The hierarchical filtering processes often used in crystal structure prediction demand a variety of approaches with differing degrees of computational cost and accuracy. We will discuss strategies including density-corrected DFT and embedding approaches that combine GGA/hybrid functional treatments of the periodic crystal with local corrections computed using more advanced functionals or correlated wave function methods.

DFT delocalization error in organic molecular crystal structure prediction: Impacts and solutions

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