The goal of this work is to develop a fundamental formalism able to translate crystallographic information (contact distance and angle) into an accurate evaluation of whether a given pair of atoms participates in a hydrogen-bond or a van der Waals interaction, and, if so, what is its energy. The problem was tackled by using the enormous amount of structural data stored in the Cambridge Crystallographic Database. The distance and angle geometrical parameters were chosen for characterisation of non-covalent atom-atom contacts. Such contacts were searched within ' some pre-defined ranges of distance and angle and consequently arranged into a two-dimensional matrix form of contact counts against distance and angle. This distance/angle contact distribution matrix was fitted with a custom-designed two-dimensional analytical function, whose general form is a superposition of two terms: one describing maxima of contact density at short distances and the other capturing the continuum of disordered long-distanced contacts. The proposed analytical solution allows: 1) analysis of the statistics of short-distance contacts separately from the background noise; 2) the evaluation of analytical functions for the calculation of the probability of a contact to be a short-distance contact; 3) calculation of a pairwise statistical mean force potential through which the interaction energy of a contact can be evaluated. !twas demonstrated that the statistical mean force potential correlates well with the quantum chemically calculated energies of molecular complexes, and thus can serve as a reliable and simple means to estimate the strength of a hydrogen' bond or a van der Waals contact, provided that the contact distance and angle are known.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:680236 |
| Date | January 2014 |
| Creators | Oliferenko, P. |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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