Crystal structure of a new polar borate Na2Ce2[BO2(OH)][BO3]2 · H2O with isolated boron triangles
- Authors: Topnikova A.P.1, Belokoneva E.L.1, Dimitrova O.V.1, Volkov A.S.1
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Affiliations:
- Faculty of Geology
- Issue: Vol 61, No 6 (2016)
- Pages: 940-944
- Section: Structure of Inorganic Compounds
- URL: https://journals.rcsi.science/1063-7745/article/view/190381
- DOI: https://doi.org/10.1134/S1063774516060171
- ID: 190381
Cite item
Abstract
Crystals of a new polar borate Na2Ce2[BO2(OH)][BO3]2 · H2O were prepared by hydrothermal synthesis. The crystals are orthorhombic, a = 7.2295(7) Å, b = 11.2523(8) Å, c = 5.1285(6) Å, Z = 2, sp. gr. C2mm (Amm2), R = 0.0253. The formula of the compound was derived from the structure determination. The Ce and Na atoms are coordinated by nine and six O atoms, respectively. The Ce position is split, and a small amount of Ce is incorporated into the Na1 site with the isomorphous substitution for Na. The anionic moieties exist as isolated BO3 and BO2(OH) triangles. The planes of the BO2(OH) triangles with mm2 symmetry are parallel to the ab plane. The planes of the BO3 triangles with m symmetry are perpendicular to the ab plane and are rotated in a diagonal way. The splitting of the Ce positions and the polar arrangement of the BO2(OH) triangles, water molecules, and Na atoms are observed along the polar a axis. The new structure is most similar to the new borate NaCa4[BO3]3 (sp. gr. Ama2), in which triangles of one type are arranged in a polar fashion along the c axis. Weak nonlinear-optical properties of both polar borates are attributed to the quenching of the second-harmonic generation due to the mutually opposite orientation of two-thirds of B triangles in the unit cell.
About the authors
A. P. Topnikova
Faculty of Geology
Email: elbel@geol.msu.ru
Russian Federation, Moscow, 119992
E. L. Belokoneva
Faculty of Geology
Author for correspondence.
Email: elbel@geol.msu.ru
Russian Federation, Moscow, 119992
O. V. Dimitrova
Faculty of Geology
Email: elbel@geol.msu.ru
Russian Federation, Moscow, 119992
A. S. Volkov
Faculty of Geology
Email: elbel@geol.msu.ru
Russian Federation, Moscow, 119992