Abstract
We present an overview of procedures that have been developed to compute several energetic quantities associated with noncovalent interactions. These formulations involve numerical integration over appropriate electronic densities. Our focus is upon the electrostatic interaction between two unperturbed molecules, the effect of the polarization of each charge distribution by the other, and the total energy of interaction. The expression for the latter is based upon the Hellmann-Feynman theorem. Applications to a number of systems are discussed; among them are dimers of uracil and interacting pairs of molecules in the crystal lattice of the energetic compound RDX.
Highlights
Noncovalent interactions are ubiquitous: between enzymes and substrates, in hydrogen bonding, physical adsorption, solvation, condensation processes, etc
Among the ten (H2O)2 calculations, the largest difference in Epol was 0.41 kcal/mole, between HF/6-31G(d,p)//6-31G(d,p) and HF/ccpVDZ//6-31G(d,p). We have extended these studies to some larger systems, the first of which was the dimer of uracil (1)
In which V0 represents the electrostatic potential at the nucleus due to the electrons
Summary
Noncovalent interactions are ubiquitous: between enzymes and substrates, in hydrogen bonding, physical adsorption, solvation, condensation processes, etc. It suffers from the fact that ∆Estab is typically several orders of magnitude smaller than EM and the EMi ; barring fortuitous cancellation, any errors in these quantities will be greatly magnified in ∆Estab. This problem can be minimized by computing EM and the EMi at high levels of accuracy, but this is likely to be prohibitively expensive in terms of processing resources for many systems of practical interest
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