Molecular modeling - Theoretical basis (part 2)

The aim here is to present in greater detail the range of quantum chemical methods, which includes Hartree-Fock and post-Hartree-Fock methods on the one hand, and methods based on DFT (Density Functional Theory) on the other. Within the DFT framework, the so-called Kohn-Sham method has recently enabled a real breakthrough in theoretical chemistry, bringing a considerable reduction in the computation time of a very precise solution of the polyelectronic Schrödinger equation for polyatomic assemblies. In recent years, DFT has come to be used routinely in the laboratory, and has established itself as a powerful guide in synthetic chemistry, for example, for predicting the products of reactions, their operating conditions and even their kinetics, and also in analytical chemistry as an irreplaceable tool for interpreting structural and spectroscopic characterizations.

This is complemented by considerations on the choice of wave functions and the theoretical characterization of chemical bonding, designed to introduce the practitioner to the options presented by the calculation codes he will wish to implement.

Finally, we offer a perspective on the "hybrid" methods currently under development, which combine classical mechanics and quantum mechanics to increase the size and hence the representativeness of atomistic models.

This dossier follows on from the on the theoretical foundations of molecular modeling. This is introduced by a few general considerations, then presents the basic notions of statistical physics, molecular mechanics and quantum mechanics required to situate the scientific basis of contemporary numerical methods for molecular modeling and simulation. A third dossier will show how the results of calculations carried out on a microscopic scale, i.e. on a representative sample of interacting atoms, can be linked to properties that can be measured on our macroscopic scale on the real material systems that the engineer wishes to control.