Intermolecular potentials potential energy surfaces , water

The multidimensional potential energy surface was written as the sum of a gas-phase (LEPS) energy surface incorporating the main features of the one-dimensional double-well potential in Example 10.1, solvent-solute interactions described by Lennard-Jones potentials with added (Coulomb) interactions corresponding to point charges, and solvent solvent interactions including intermolecular degrees of freedom. The solvent consisted of 64 water molecules. 

Between the wall of the cell and any ions (H+, H30+, H502+) forces of supermolecular hydrogen P-bonds and electrostatic y-bonds operate (see Fig. 2). Surfaces of intermolecular potential energy have been calculated by density functional method stated in our paper [6], Necessary data about spatial distributions of electron charge density inside framework of aqua multiparticle had been taken from calculations of aquatic ions and the ring of water (H20)n by using of standard molecular orbital method in the minimal basis set (STO-3G). Results of calculations are shown in Table 1. 

Clementi (1985) described ab initio computational chemistry as a global approach to simulations of complex chemical systems, derived directly from theory without recourse to empirical parametrizations. The intent is to break the computation into steps quantum mechanical computations for the elements of the system, construction of two-body potentials for the interactions between them, statistical mechanical simulations using the above potentials, and, finally, the treatment of higher levels of chemical complexity (e.g., dissipative behavior). This program has been followed for analysis of the hydration of DNA. Early work by Clementi et al. (1977) established intermolecular potentials for the interaction of lysozyme with water, given as maps of the energy of interaction of solvent water with the lysozyme surface. 

For liquids and solids, specific orientation and conformation of msymmetrical molecules (ions) in the interfacial regions result not only in the maximization of their interaction energy, but also yield entropy effects that cannot be neglected. For example, molecular dynamics calculations of the intermolecular potential function points to a predominant orientation of the water dipoles at the Liquid-Gas interface [45]. Other examples are an icelike structuring of water molecules in the vicinity of crystalline solid surfaces [46] and a specific orientation of the alcohol molecules in the interface between a liquid n-alkanol and water [47]. 

Wallqvist A, Ahlstrom P, Karlstrom G (1990) A new intermolecular energy calculation scheme -applications to potential surface and liquid properties of water. J Phys Chem 94(4) 1649-1656... 

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