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An optimized intermolecular force field for hydrogen‐bonded organic molecular crystals using atomic multipole electrostatics
Author(s) -
Pyzer-Knapp Edward O.,
Thompson Hugh P. G.,
Day Graeme M.
Publication year - 2016
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520616007708
Subject(s) - sublimation (psychology) , intermolecular force , electrostatics , multipole expansion , force field (fiction) , chemistry , chemical physics , lattice energy , molecular dynamics , partial charge , crystal (programming language) , molecule , computational chemistry , molecular physics , atomic physics , crystal structure , crystallography , physics , organic chemistry , quantum mechanics , psychology , computer science , programming language , psychotherapist
We present a re‐parameterization of a popular intermolecular force field for describing intermolecular interactions in the organic solid state. Specifically we optimize the performance of the exp‐6 force field when used in conjunction with atomic multipole electrostatics. We also parameterize force fields that are optimized for use with multipoles derived from polarized molecular electron densities, to account for induction effects in molecular crystals. Parameterization is performed against a set of 186 experimentally determined, low‐temperature crystal structures and 53 measured sublimation enthalpies of hydrogen‐bonding organic molecules. The resulting force fields are tested on a validation set of 129 crystal structures and show improved reproduction of the structures and lattice energies of a range of organic molecular crystals compared with the original force field with atomic partial charge electrostatics. Unit‐cell dimensions of the validation set are typically reproduced to within 3% with the re‐parameterized force fields. Lattice energies, which were all included during parameterization, are systematically underestimated when compared with measured sublimation enthalpies, with mean absolute errors of between 7.4 and 9.0%.