## out-of-plane bending coordinate

in molecular geometry
https://doi.org/10.1351/goldbook.O04354
Given by $\Delta \theta _{i- jkl}=\frac{\Delta z_{j}}{r_{eij}}\ \sin \mathit{\Phi }_{kil}$ where the numbering of the atoms is given in the diagram. $$\mathit{\Phi} _{kil}$$ denotes
O04354.png
the @A00346@ between the bonds $$ik$$ and $$il$$, $$\Delta z_{j}$$ the perpendicular distance of the atom $$j$$ from the instantaneous plane $$ikl$$ and $$r_{eij}$$ the equilibrium length of the bond $$ij$$.
Source:
PAC, 1978, 50, 1707. (Definition and Symbolism of Molecular Force Constants) on page 1710 [Terms] [Paper]