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Birefringence, as a fundamental parameter of optical crystals, plays a vital role in numerous optical applications such as phase modulation, light splitting, and polarization, thereby making them key materials in laser science and technology. The significant birefringence of vanadate polyhedra provides a new approach for developing birefringent materials. In this study, first-principles calculations are used to investigate the band structures, density of states (DOS), electron localization functions (ELFs), and birefringence behaviors of four alkali metal vanadate crystals AV3O8 (A = Li, Na, K, Rb). The computational results show that all AV3O8 crystals have indirect band gaps, whose values are 1.695, 1.898, 1.965, and 1.984 eV for LiV3O8, NaV3O8, KV3O8, and RbV3O8, respectively. The DOS analysis reveals that near the Fermi level, the conduction band minima (CBM) in these vanadates are predominantly occupied by the outermost orbitals of V atoms, while the valence band maxima (VBM) are primarily contributed by O-2p orbitals. The O-2p orbitals also exhibit strong localization near the Fermi level. Combined with highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) analysis and population analysis, the bonding interactions in all four crystals mainly arise from the hybridization between V-3p and O-2p orbitals, indicating strong covalent bonding in V—O bonds. Through the analysis of structure-property relationships, the large birefringence is primarily attributed to the pronounced structural anisotropy, high anisotropy index of responsive electron distribution, unique arrangement of anionic groups, and d-p orbital hybridization between V-3d and O-2p orbitals. The calculated birefringence values at a wavelength of 1064 nm for LiV3O8, NaV3O8, KV3O8, and RbV3O8 are 0.28, 0.30, 0.28, and 0.27, respectively.
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Keywords:
- alkali metal vanadate /
- first principles /
- electronic structure /
- birefringence
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] -
Compounds a/nm b/nm c/nm β/(°) b/c Error V/nm3 LiV3O8 Before 0.668 0.360 1.203 107.830 0.299 1.67% 0.275 After 0.695 0.358 1.219 108.397 0.294 0.288 NaV3O8 Before 0.512 0.855 0.744 101.993 1.148 3.92% 0.319 After 0.531 0.877 0.795 113.173 1.103 0.350 KV3O8 Before 0.500 0.839 0.767 98.135 1.094 4.84% 0.319 After 0.516 0.865 0.831 103.812 1.041 0.361 RbV3O8 Before 0.501 0.842 0.791 96.943 1.064 2.16% 0.331 After 0.516 0.865 0.831 100.581 1.041 0.365 
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Substance Species Atomic population Total Charge/e Bond Bond
populationLength/Å s p d LiV3O8 Li –0.20 0.00 0.00 –0.20 1.20 Li—O –0.06 2.16 V 0.20 0.31 3.20 3.71 1.29 O—V 0.01 2.86 O 1.90 4.68 0.00 6.59 –0.59 O—V 0.92 1.66 NaV3O8 Na 2.07 5.95 0.00 8.01 0.99 Na—O 0.02 2.38 V 0.15 0.33 3.18 3.66 1.34 O—V 0.92 1.64 O 1.89 4.72 0.00 6.62 –0.62 O—V 0.33 1.99 KV3O8 K 2.03 5.91 0.00 7.95 1.05 K—O 0.04 2.72 V 0.15 0.34 3.32 3.72 1.28 O—V 0.97 1.64 O 1.89 4.74 0.00 6.63 –0.63 O—V 0.33 1.98 RbV3O8 Rb 2.04 5.86 0.00 7.90 1.10 Rb—O 0.04 2.97 V 0.16 0.35 3.23 3.74 1.26 O—V 0.98 1.64 O 1.89 4.74 0.00 6.64 –0.64 O—V 0.34 1.98
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Compounds Groups δ Δn LiV3O8 VO4 0.011 0.28 NaV3O8 V3O8 0.019 0.30 KV3O8 V3O8 0.013 0.28 RbV3O8 V3O8 0.012 0.27
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[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64]
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