Field energy

Hamiltonian = t+ The additivity of implies that the mean-field energies il/are additive and the wavefunctions [Pg.2162]

The following sections give an overview of the functional form of the PFF and a short explanation of the various contributions to the total force field energy of a molecule or molecular system. 

The force constants in the equations are adjusted empirically to repro duce experimental observations. The net result is a model which relates the "mechanical" forces within a stmcture to its properties. Force fields are made up of sets of equations each of which represents an element of the decomposition of the total energy of a system (not a quantum mechanical energy, but a classical mechanical one). The sum of the components is called the force field energy, or steric energy, which also routinely includes the electrostatic energy components. Typically, the steric energy is expressed as... 

The force field energy is written as a sum of terms, each describing the energy required for distorting a molecule in a specific fashion. 

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