Chemistry
An investigation of distortions of the dion-jacobson phase RbSr 2Nb 3O 10 and its acid-exchanged form with 93Nb solid state NMR and DFT calculations
Document Type
Article
Abstract
The different niobium sites in a Dion-Jacobson triple-layered perovskite, RbSr 2Nb 3O 10, and its acid-exchanged version, HSr 2Nb 3O 10, were investigated by using solid state NMR and DFT methods. 93Nb electric field gradient (EFG) and chemical shift anisotropy (CSA) tensor values were extracted and site assignments made by using DFS, VOCS, MQMAS, and {1H}- 93Nb CP NMR techniques. The exterior niobium site exhibited a quadrupolar coupling (CQ) of 45 MHz and a CSA span of 820 ppm while the interior site exhibited a Reverse trend with a CQ of 93 MHz and a CSA span of 530 ppm. Both EFG and CSA tensors for the sites exhibited near axial symmetry although the CSA tensors had a greater deviation. The symmetry of the tensors is in conflict with the pReviously proposed structure for RbSr 2Nb 3O 10 and implies a lower symmetry space group and a possible tilting of the octahedra. Acid exchange altered the EFG tensors for both sites reducing their CQ values to 39 and 86 MHz, respectively, while not substantially changing the tensor symmetry. The effect on the CSA tensor occurred only for the surface site with the span reduced to 560 ppm. The effect of the tilting of the octahedra and alteration of bond angles and bond lengths on the EFG tensor was investigated through periodic DFT calculations. Interior and exterior sites of the rubidium form exhibited different tilt along the c-axis of 14° and -3°, respectively, based on the 93Nb EFG values. Calculations on the acid-exchanged composition implied that structural alterations must occur with both sites. The exterior octahedra experience changes in both bond length and bond angles, while only a subtle elongation of the interior site is found. © 2009 American Chemical Society.
Publication Title
Journal of Physical Chemistry C
Publication Date
10-21-2009
Volume
113
Issue
40
First Page
17548
Last Page
17559
ISSN
1932-7447
DOI
10.1021/jp902318v
Keywords
acids, bond length, chemical shift, electric currents; Electric field effects; Light polarization; Magnetic anisotropy; Niobium; Nuclear magnetic resonance, oxide minerals, Perovskite, probability density function, rubidium, single crystals, sulfur compounds
Repository Citation
Wang, Xuefeng; Adhikari, Jhashanath; and Smith, Luis J., "An investigation of distortions of the dion-jacobson phase RbSr 2Nb 3O 10 and its acid-exchanged form with 93Nb solid state NMR and DFT calculations" (2009). Chemistry. 56.
https://commons.clarku.edu/chemistry/56
