Hydrogen bonds and elastic anisotropy of nitrile molecular crystals: an investigation from first-principles

ABSTRACT

Atomistic calculations based on semi-classical dispersion-corrected density functional theory were performed to investigate bonding and elastic properties of low temperature polymorphs of three nitrile molecular crystals. For that purpose, the DFT-PBE-D3ijk method, which account for both pair and three-body interactions, was applied. The analysis of Hirshfeld surfaces demonstrated that the (C-N…H) hydrogen bonds are the strongest and the dominant ones in the three nitrile molecular crystals. The latter were found to share a common structural feature, consisting of an antiparallel orientation of the terminal nitrile groups at their constituent molecules. Our prediction of the elastic properties demonstrated that malonitrile has the highest Young modulus and succinonitrile has the lower one. The three nitrile crystals are expected to have similar resistance to volume variation while succinonitrle is predicted to exhibit the lowest resistance to shape change. Otherwise, succinonitrile was found to be ductile while malononitrile and acetonitrile were shown to be brittle. Elasticity anisotropy analysis demonstrated that the directions of maximum Young’s modulus are always nearly parallel to the direction of alignment of strong (C-H…N) hydrogen bonds in the three nitrile crystals. The present analyses are relevant for understanding the structure and the properties of more complex high temperature phases.

KEYWORDS:

• Nitrile molecular crystals
• hydrogen bonds
• DFT-D
• elasticity
• anisotropy

Acknowledgements

I.B and G.C acknowledge the University of Bejaia and the Algerian Ministry of High Education and Scientific Research for financial support (PRFU: B00L02UN060120200001). La direction Générale de la Recherche Scientifique et du Développement Technologique (DGRSDT) is also acknowledged for funding. Dr. J.M Carlsson (BIOVIA – Dassault Systèmes) is acknowledged for fruitful discussions. The calculations were carried out at the HPC centre of the university of Biskra (Algeria) and the HPC centre of the university of Constantine (Algeria).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Algerian Ministry of High Education and Scientific Research [grant number B00L02UN060120200001].