Less computationally demanding approximations have been developed to estimate the binding energy of molecules. The most frequently used is molecular mechanics (force fields) . The idea is to describe the complex multi-atomic system of a molecule using classical physics. The most common force fields involve potential energy, torsional conditions, bond geometry, electrostatic conditions and the Lenard-Jones potential. Examples of force fields are MMFF94, CHARMM, AMBER, and GRO-MACS .