The First High‐Pressure Chromium Oxonitridoborate CrB₄O₆N—an Unexpected Link to Nitridosilicate Chemistry

Abstract

CrB4O6N crystallizes in the non‐centrosymmetric space group P63mc (no. 186) with the lattice parameters a=5.1036(1), c=8.3519(3) Å, and a volume of 188.40(1) Å3. It was synthesized in a high‐pressure/high‐temperature experiment at 7 GPa and 1673 K and represents the first high‐pressure oxonitridoborate. It is built up of starlike‐shaped entities of four BO3N tetrahedra, connected via one common nitrogen atom that resembles the fourfold‐coordinated nitrogen atoms in the homeotypic nitridosilicates MYbSi4N7 (M=Sr, Ba). Building up a network with channels that contain the Cr3+ ions, CrB4O6N contains for the first time a tetrahedral building unit in contrast to trigonal planar B(O/N)3 entities in all other known oxonitridoborates. The structural relations as well as the results of spectroscopic measurements and calculations on the chromium oxonitridoborate are discussed.

Nitrides: a promising class of nonlinear optical material candidates

“…The synthesis and physical properties (including SHG performance) of CrB 4 O 5 N were investigated in 2021 by Huppertz et al . 79 CrB 4 O 5 N crystallizes in hexagonal space group P 6 3 mc . Interestingly, the structure of the chromium oxonitridoborate CrB 4 O 5 N is similar to that of the nitridosilicates SrYSi 4 N 7 .…”

Review of Heteroleptic Tetrahedra as Birefringent or Nonlinear Optical Motifs

“…Second, for oxy-tetrahedra MO 4 (M = B, Ga, Si, Ge, P, As), their O atoms can be partially substituted the N or S atoms to produce the heteroleptic tetrahedra MO x X 4– x (M = B, Ga, Si, Ge, P, As; X = N, S; x = 1, 2, 3). In these heteroleptic tetrahedra, it has been verified through first-principles calculations and experimental methods that oxonitridosilicates with SiO 4– x N x ( x = 1, 2, 3) and oxythiophosphates with PO 4– x S x ( x = 1, 2, 3) can be used as ultraviolet NLO materials to maintain a balance between birefringence and NLO coefficients. , Especially, the heteroleptic tetrahedron BO 3 N exists in high-pressure oxonitridoborate CrB 4 O 6 N, and its crystal structure is built up the starlike-shaped entities of the four BO 3 N tetrahedra . BO 3 N has large polarizability anisotropy of 6.9 au, high hyperpolarizability of 79.6 au, and a large HOMO-LUMO energy gap of 8.2 eV (Table S1), which means that it is a potential ultraviolet birefringent or NLO functional optical motif.…”

“…43,44 Especially, the heteroleptic tetrahedron BO 3 N exists in high-pressure oxonitridoborate CrB 4 O 6 N, and its crystal structure is built up the starlike-shaped entities of the four BO 3 N tetrahedra. 97 BO 3 N has large polarizability anisotropy of 6.9 au, high hyperpolarizability of 79.6 au, and a large HOMO-LUMO energy gap of 8.2 eV (Table S1), which means that it is a potential ultraviolet birefringent or NLO functional optical motif. For heteroleptic tetrahedral AsO 4−x S x (x = 1, 2) and PO 4−x N x (x = 1, 2, 3), they possess large optical anisotropy and the wide HOMO-LUMO energy gaps, which are close to those of SiO 4−x N x (x = 1, 2, 3) and PO 4−x S x (x = 1, 2, 3) (Table S1).…”

Real Competitors to Ruby: The Triel Oxonitridoborates AlB4O6N, Al0.97Cr0.03B4O6N, and Al0.83Cr0.17B4O6N

“…The title compounds are isotypic to CrB 4 O 6 N, [10] which itself is homeotypic to the ambient pressure nitridosilicates MYbSi 4 N 7 (M = Sr, Ba, Eu). [10,11] The latter crystallize in the NaBe 4 SbO 7 structure type (swedenborgite).…”