Strong Orbital Interaction in pi-pi Stacking System
  A simple prototypical model of aromatic pi-pi stacking system -- benzene sandwich dimer is investigated by ab initio calculations based on second-order Moller-Plesset perturbation theory (MP2) and Minnesota hybrid functional M06-2X. 
Xiao-Xiao Fu, Jian-Fu Li, and Rui-Qin Zhang
physics.atm-clus