Empirical Energy Functions

XPLOR's empirical energy function has the general form

The sum is carried out over all double selections of atoms (see Section 4.7) with weights . The default for the double selections is one double selection involving all atoms with unity weights. The first four terms in Eq. 4.3 are conformational energy terms.

The remaining five terms in Eq. 4.3 describe nonbonded interactions. The term describes the non-symmetry-related van der Waals energy, describes the non-symmetry-related electrostatic energy, describes the van der Waals energy between symmetry-related atoms, and describes the symmetry-related electrostatic energy. The term describes an explicit hydrogen-bonding energy. This term is used only in older parameter files.

In the next sections, the empirical energy terms are described in more detail.