internal valence force field

Acronym: IVFF

A force field expressed in terms of bond-stretching, angle-bending, torsional and other displacements directly connected to the structural parameters of the molecule:
V = 1 2 ∑ k i j R i R j
or
V = 1 2 ∑ K i j R i R j
where k (or K) are the force constants and R the internal valence coordinates.
Source:
PAC, 1978, 50, 1707 (Definition and symbolism of molecular force constants) on page 1709