Effect of the tetrahedral groups on the optical properties of LaBRO5 (R = Si and Ge): A first-principles study

Abstract

As potential candidates for deep-UV nonlinear optical (NLO) crystals, borosilicates and borogermanates, which contain NLO-active groups such as B-O, Si-O, and Ge-O groups, have fascinated many material scientists' research enthusiasm. In this paper, the electronic structures and optical properties of two isostructural noncentrosymmetric crystals LaBRO5 (R = Si and Ge) have been studied by the first-principles method. Combined with the analyses of the SHG-density and the localized electron-density difference, contributions of the constituent tetrahedra to the total NLO responses are investigated. Eventually, BO4 and GeO4 groups give nearly equal contributions to the SHG effect of LaBGeO5, but for LaBSiO5, SiO4 groups express stronger SHG response than that of BO4. Such interesting conclusion is consistent with the distortion index analyses and dipole moment.

Ba4Bi2(Si8−xB4+xO29) (x = 0.09): a new acentric metal borosilicate as a promising nonlinear optical material

“…The anionic borosilicate framework in LnBSiO 5 (Ln = La, Ce, Nd) is also solely composed of BO 4 and SiO 4 tetrahedral groups 37. However, the BO 4 and SiO 4 arrange in a different way.…”

Discovery of excellent ultraviolet nonlinear optical materials in chlorates and bromates with highly stereochemically active lone pairs

“…The band gaps of alkali metal/alkaline earth metal chlorates are as wide as 6.8–7.0 eV, being comparable to or larger than those of some classical borates, such as K 2 Al 2 B 2 O 7 (6.89 eV), CsLiB 6 O 10 (6.89 eV), Cs 2 Al 2 (B 3 O 6 ) 2 O (7.05 eV), Rb 3 Ba 3 Li 2 Al 4 B 6 O 20 F (6.26 eV), K 3 Sr 3 Li 2 Al 4 B 6 O 20 F (6.53 eV), LaBGeO 5 (6.40 eV), the well-known UV NLO crystal β-BaB 2 O 4 (6.43 eV), etc . 51–56 Hence, they are all deep-UV transparent, which is the most important requirement for DUV NLO materials. For alkali metal/alkaline earth metal bromates, the band gaps range from 5.65 to 6.18 eV, comparable to or larger than many carbonates, such as ABCO 3 F (A = alkali metal, B = alkaline earth metal, ∼6.20 eV), Cs 3 Ba 4 (CO 3 ) 3 F 5 (5.90 eV), [C(NH 2 ) 3 ] 2 Zn(CO 3 ) 2 (5.90 eV), Zn(NH 3 )CO 3 (6.08 eV), NaZnCO 3 F (4.61 eV), Na 4 Zn(CO 3 ) 3 (4.06 eV), etc .…”

“…3a (6.40 eV), the wellknown UV NLO crystal β-BaB 2 O 4 (6.43 eV), etc. [51][52][53][54][55][56] Hence, they are all deep-UV transparent, which is the most important requirement for DUV NLO materials. For alkali metal/alkaline earth metal bromates, the band gaps range from 5.65 to 6.18 eV, comparable to or larger than many carbonates, such as ABCO 3 F (A = alkali metal, B = alkaline earth metal, ∼6.20 eV), Cs 3 Ba 4 (CO 3 ) 3 F 5 (5.90 eV), [C(NH 2 ) 3 ] 2 Zn(CO 3 ) 2 (5.90 eV), Zn (NH 3 )CO 3 (6.08 eV), NaZnCO 3 F (4.61 eV), Na 4 Zn(CO 3 ) 3 (4.06 eV), etc.…”