posted on 2024-01-14, 14:03authored byXueting Pan, Junben Huang, Yineng Huang
Birefringent crystals
assume a pivotal role in the realm
of optical
materials, because of their capacity to manipulate the polarization
state of light waves. Herein, the first-principles high-throughput
screening methodology was implemented to search for materials with
large birefringence (Δn > 0.1), and 15 compounds
were highlighted from 102 d0-transition
metal oxyhalides AOmXn (A = V, Nb, Mo, W; X
= F, Cl, Br, I; m and n = integers). Notably, 12 compounds exhibit
large birefringences (Δn > 0.14 at 1064
nm),
four of them (MoO2Br2, WOBr4 and
NbOX2 (X = Br, I)) even larger than 0.6 at 1064 nm, surpassing
those of YVO4 (Δn = 0.21 at 1064
nm) and TiO2 (Δn = 0.256 at 1530
nm), the well-known commercial birefringent materials. Additionally,
the nonlinear optical coefficients of 8 noncentrosymmetric compounds
in the 15 compounds were also calculated. However, most of them have
small nonlinear optical coefficients, except WOBr4 (d15 = −15.01 pm/V), which is 1.1 times
that of the infrared benchmark AgGaS2 (d36 = 13.4 pm/V). The exploration of the d0-transition metal oxyhalides AOmXn with exceptionally large birefringence sets a direction in future
searches for birefringent crystals.