How does Ccomputational Chemistry work?

Simply put, use mathmatic expression to describe the movements of electron and nucleus before, during and after the reaction.

There are three primary subdisciplines: (A) structure theory, (B) molecular dynamics and (C) statistical mechanics.

(A) Electronic structure theory describe the motions of the electrons and produces energy surfaces. Here is an example of energy surface:

(B) Molecular and chemical dynamics describes the motions of the atoms within the molecule and the surrounding solvent.

The collision among molecules and resulting energy transfers among translational, vibrational, rotational, and electronic modes, as well as chemical reactions that occur intramolecularly or in bi-molecular encounters lie within the realm of molecular and chemical dynamic theory.

(C) Statistical mechanics provide the framework for studying large collections of molecules and tells us how to average over positions and velocities to properly simulate the laboratory distribution of molecues.

(Z) Something deep: the fluctuation-dissipation theorem is an exact relation between the static correlation function and the time-dependent response of the system, and semiclassical techniques provide a simple ansatz for approximating quantum results using essentially classical information.