Overcoming the difficulties of predicting conformational polymorph energetics in molecular crystals <i>via</i> correlated wavefunction methods
Chandler Greenwell, Jessica L. McKinley, Peiyu Zhang, Qun Zeng, Guangxu Sun, Bochen Li, Shuhao Wen, Gregory J. O. Beran
Abstract
-acetamidobenzamide, ROY, and oxalyl dihydrazide are examined in detail. DFT functionals that have previously been very successful in crystal structure prediction perform poorly in all three systems, due primarily to the poor intramolecular conformational energies, but also due to the intermolecular description in oxalyl dihydrazide. In all three cases, a fragment-based dispersion-corrected second-order Møller-Plesset perturbation theory (MP2D) treatment of the crystals overcomes these difficulties and predicts conformational polymorph stabilities in good agreement with experiment. These results highlight the need for methods which go beyond current-generation DFT functionals to make crystal polymorph stability predictions truly reliable.