Poly(difluorophosphazene) as the First Deep-Ultraviolet Nonlinear Optical Polymer: A First-Principles Prediction.

A novel concept to obtain the deep-ultraviolet (DUV) nonlinear optical (NLO) materials is proposed based on the assembling of one-dimensional (1D) polar motifs into quasi-1D polymer patterns. Based on the first-principles calculations, we have successfully discovered an excellent DUV NLO polymer, i.e., poly(difluorophosphazene), with the chemical formula of (PNF2 )n . Calculations reveal that PNF2 has a larger band gap, a stronger second harmonic generation effect, a larger birefringence, and a shorter phase-matching cutoff than KBe2 BO3 F2 . These findings not only demonstrate that the PNF2 is the first reported DUV NLO polymer, but also could open a new direction to discover novel DUV NLO materials in polymer systems.