Ab initio fragment orbital theory (AFOT): application to some two-photon-absorbing (TPA) molecules

The recently developed AFOT code is applied to investigate the two-photon-absorbing (TPA) properties of some of the bis(styryl) benzene derivatives (BSBD) demonstrated recently to possess large TPA cross sections. The results are compared both with the earlier semi-empirical as well as the more recent density functional calculations.