Excellent Infrared Nonlinear Optical Crystals BaMO(IO3)5 (M = V, Ta) Predicted by First Principle Calculations

Two nonlinear optical crystals, BaVO(IO3)5 and BaTaO(IO3)5, are designed by substituting Nb with V and Ta, respectively, in BaNbO(IO3)5, which is itself a recently synthesized infrared nonlinear optical (NLO) material. The designs of BaVO(IO3)5 and BaTaO(IO3)5 from BaNbO(IO3)5 are based on the following motivation: BaVO(IO3)5 should have a larger second-harmonic generation (SHG) coefficient than BaNbO(IO3)5, as V will result in a stronger second-order Jahn-Teller effect than Nb due to its smaller ion radius; at the same time, BaTaO(IO3)5 should have a larger laser-damage threshold, due to the fact that Ta has a smaller electronegativity leading to a greater band-gap. Established on reliable first-principle calculations, it is demonstrated that BaVO(IO3)5 has a much larger SHG coefficient than BaNbO(IO3)5 (23.42 × 10−9 vs. 18.66 × 10−9 esu); and BaTaO(IO3)5 has a significantly greater band-gap than BaNbO(IO3)5 (4.20 vs. 3.55 eV). Meanwhile, the absorption spectra and birefringences of both BaVO(IO3)5 and BaTaO(IO3)5 are acceptable for practice, suggesting that these two crystals can both be expected to be excellent infrared NLO materials.