Improper Torsion Functions

Improper torsion angles deal with out-of-plane bending modes within molecules. In Dissolve, any valid torsion potential can be used for an improper. Note that in Dissolve the central atom of the quartet is denoted as $i$.

Improper torsion interaction between atoms $i$, $j$, $k$ and $l$, where the improper angle ${\varphi }_{ijkl}$ can be viewed as the angle made between the two planes defined by $i$-$j$-$k$ and $j$-$k$-$l$.