Chained Interactions

A. Lobato
MALTA-Consolider Team, Departamento de Química-Física I Universidad Complutense, Madrid, Espagne.
Mercredi 15 Juin 2016, 11h00
bibliothèque LCT, tour 12 - 13, 4^ème étage

The concept of chemical bond is one of the main pieces of the chemical language. It summarizes our knowledge about the structure, geometry, stability, and reactivity of substances. Being one of the cornerstones of chemistry, it has logically suffered conceptual shifts as it became more and more systematized. Nevertheless these definitions are limited to the equilibrium configurations of isolated molecules or to reaction pathways in supermolecules. Little is known about the evolution of interactions far from equilibrium molecular geometries. This fact has obvious origins, for chemists do not observe easily systems frozen at such exotic geometries. After all, our world is one at near room pressure and temperature. The presence of non-nuclear maxima, atomic radii definitions of high pressure phenomena as the polymerization of CO are only some examples of a universal bonding sequence.
The aim of this work is to abound on these issues, trying to gather a number of loose facts into the seed of a universal model of the chemical bond between a given pair of atoms, valid in wide ranges of internuclear distances. Here we present a simple model based on a pair potential approach and spinodal criteria, which reveals the existence of three characteristics distances which summarizes the form of a given interaction and define the stability range of the next interaction resembling the idea that the interactions are chained. To test our model we have analyzed the different interactions of liquid water (covalent, Electrostatic and Dispersive). By comparing radial distribution functions, Raman spectroscopy and bond valence strength we will show how a simple model is able to explain the general features of bonding in such system, and more on how the interactions spread with distance. Finally we analyzed the intermolecular non-contact histograms available in the Cambridge Structural Database evidencing that the universal pattern of well-defined maxima and minima can be understood in terms of the spinodal criteria and chained interactions.

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