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

Abstract

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 KBe2BO3F2. 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.

Ag4Hg(SeO3)2(SeO4): a novel SHG material created in mixed valent selenium oxides by in situ synthesis

“…S4). Ag (2) and Ag (3) (3) is in a SeO 4 tetrahedral coordination with the Se-O bonds limited in 1.62(2)-1.65(2) Å ( Fig. S6), which are consistent with the reported selenium oxides [8][9][10][11][12][13].…”

“…The deviation of Ag/Hg(1) from the ideal oxidation is mainly due to the low BVS of Ag atom, which is common in silver oxides [45][46][47][48][49]. The slightly higher valence for Se (2) can be attributed to the two short Se-O bonds (1.645 Å). Ag 4 Hg(SeO 3 ) 2 (SeO 4 ) (1) To elucidate the structure more clearly, the bonds of Ag(2) and Ag (3) were left out.…”

“…Design and syntheses of noncentrosymmetric (NCS) structures have received widespread attention due to their valuable physical properties, such as ferroelectric, pyroelectricity, piezoelectricity and second harmonic generation (SHG), which cannot be found in centrosymmetric (CS) compounds [1][2][3][4]. Selenites are a kind of important lone-pair oxyanions, of which the coordination environments are inherently polar, with the oxygen ligands situated at one side of the cations, due to the stereoactive nonbonded electron pair [5][6][7].…”

Deep-ultraviolet nonlinear optical crystals: concept development and materials discovery

“…If the E g can be further increased, the DUV NLO performance can be achieved. Accordingly, the existing poly(difluorophosphazene) (PNF 2 ) was predicted, showing larger E g (~8.8 eV), stronger d ij (~0.86 pm V −1 ), larger Δ n (~0.16) and shorter λ PM (~142 nm) than KBBF (Table 1 ) 69 . It is the first predicted chain-like polymer DUV NLO structure.…”

“…Conventional DUV NLO materials are layered fluorine-based borate anionic frameworks, since the layered frameworks favors large Δ n , and the fluorine-based borate anionic groups favor large E g . To this end, the exploration of the material is extended from borate to carbonate anionic groups, from fluorine-based to hydroxyl-based anionic groups, and from layered to chained anionic groups, respectively 69 , 70 , 76 , to enhance or implement DUV NLO properties in multiple ways.…”