I found this: http://www.schrodinger.com/kb/1556
Which states:"Pi-pi stacking: A pi-pi interaction is defined as an interaction between two aromatic rings in which either (a) the angle between the ring planes is less than 30° and the distance between the ring centroids is less than 4.0 Å (face-to-face), or (b) the angle between the ring planes is between 60° and 120° and the distance between the ring centroids is less than 5.5 Å (edge-to-face)."
Not to mention "60° and 120°". I assume they mean 60 to 90, as the angle between two planes go from 0 to 90.
Problem is that this is not a very good definition because I applied these conditions to a simulation and only 1/3 of the simulation had pi-pi stacking. This is not correct however because a majority of the rejected frames seem to be "Parallel-displaced" (http://en.wikipedia.org/wiki/Stacking_%28chemistry%29).
I don't want to make a custom definition because I want to publish these results, and to make a self made definition seems to me to be a conflict of interest.
Any ideas?
Thanks
