internal valence force field (IVFF)

https://doi.org/10.1351/goldbook.I03111
A force field expressed in terms of bond-stretching, @[email protected], torsional and other displacements directly connected to the structural parameters of the molecule: \[V=\frac{1}{2}\ \sum k_{ij}\ R_{i}\ R_{j}\] or \[V=\frac{1}{2}\ \sum K_{ij}\ R_{i}\ R_{j}\] where \(k\) (or \(K\)) are the @[email protected] and \(R\) the internal @[email protected] coordinates.
Source:
PAC, 1978, 50, 1707. (Definition and Symbolism of Molecular Force Constants) on page 1709 [Terms] [Paper]