MS22-P05 Deciphering the driving forces in crystal packings by analysis of electrostatic energies and contact enrichment ratios. Christian Jelsch (CRM2 CNRS Lorraine University, Vandoeuvre les Nancy, France) Yvon Bibila Mayaya Bisseyou (Universite Felix Houphouet-Boigny, Abidjan, Cote D'Ivoire)email: christian.jelsch@univ-lorraine.frThe decomposition of the crystal contact surface between pairs of interacting chemical species enables to derive an enrichment ratio [1,2,3]. This descriptor yields information on the propensity of chemical species to form intermolecular interactions with themselves and other species. The enrichment ratio is obtained by comparing the actual contacts in the crystal with those computed as if all types of contacts had the same probability to form.

 The enrichments and contacts tendencies were analysed in several families of compounds, based on chemical composition and aromatic character. As expected, the polar contacts of type H∙∙∙N, H∙∙∙O and H∙∙∙S, which are generally hydrogen bonds, show enrichment values larger than unity.

Hydrophobic contacts show different types of behaviour depending on the molecular content.
The electrostatic energy of  short contacts was also computed using charge density models transfered from the ELMAM2 database.
The contact enrichment ratios were statistically compared with the electrostatic energy values.
The analysis suggests that strong attractive interactions are enriched and are a driving force in the crystal packing formation.
On the other hand repulsive interactions are generally avoided or under-represented.
The behaviour of weaker interactions is less contrasted and will be discussed.

Jelsch, C., & Bibila Mayaya Bisseyou, Y. (2017). IUCrJ, 4, 158-174.

Jelsch, C., Soudani, S., & Ben Nasr, C. (2015). IUCrJ, 2, 327-340.

Jelsch, C., Ejsmont, K., & Huder, L. (2014). IUCrJ, 1(2), 119-128.

Keywords: electrostatic , contacts , enrichment
Keywords: Hirshfeld surface , charge density , molecular interactions