2. Calculation of configuration energy

The total energy of a whole is the sum of the potential energy and kinetic energy of its particles, nuclei and electrons. Quantum mechanics provides the most rigorous formal framework for evaluating all energy components. However, nuclei are sufficiently massive that, even in the case of the proton, classical mechanics provides an almost exact approximation.

Empirical force fields were developed to describe the behavior of ensembles of atoms within the framework of classical molecular mechanics, which avoids the quantum treatment of electronic energy. Potential energy is expressed as a simple analytic function of the spatial coordinates of nuclei, reduced to point masses and, where appropriate, assigned a point electric charge.