固态中的阳离子-阴离子相互作用及极性结构

Cation-anion interactions and polar structures in the solid state.

作者信息

Marvel Michael R, Lesage Julien, Baek Jaewook, Halasyamani P Shiv, Stern Charlotte L, Poeppelmeier Kenneth R

机构信息

Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA.

出版信息

J Am Chem Soc. 2007 Nov 14;129(45):13963-9. doi: 10.1021/ja074659h. Epub 2007 Oct 18.

DOI:10.1021/ja074659h

PMID:17944466

Abstract

Complicated structures where oxygen and fluorine are found together in one framework, where deviations from Pauling's second crystal rule (PSCR) are expected, often result in structures with important physical properties. The [NbOF5]2- anion and therefore all the individual Nb-O and Nb-F bonds are ordered in noncentrosymmetric KNaNbOF5 and centrosymmetric CsNaNbOF5. The Na/K- and Na/Cs-O/F interactions in these phases, in particular the expected deviations from PSCR and the bond valence model, reveal the essential role of the small potassium cations in the acentric packing of the [NbOF5]2- anion. KNaNbOF5 crystallizes in the orthorhombic and polar space group Pna21 (No. 33) with lattice constants a = 11.8653(11) A, b = 5.8826(6) A, c = 8.1258(8) A, and Z = 4, while CsNaNbOF5 crystallizes in the orthorhombic space group Pbcn (No. 60) with lattice constants a = 8.3155(7), b = 13.3176(11), c = 11.1314(9), and Z = 8.

摘要

在一个框架中同时存在氧和氟的复杂结构，预计会偏离鲍林第二晶体规则（PSCR），这类结构通常会产生具有重要物理性质的结构。在非中心对称的KNaNbOF5和中心对称的CsNaNbOF5中，[NbOF5]2-阴离子以及所有单个的Nb - O和Nb - F键都是有序排列的。这些相中Na/K - 和Na/Cs - O/F相互作用，特别是预期的与PSCR和键价模型的偏差，揭示了小的钾阳离子在[NbOF5]2-阴离子非中心堆积中的重要作用。KNaNbOF5以正交极性空间群Pna21（编号33）结晶，晶格常数a = 11.8653(11) Å，b = 5.8826(6) Å，c = 8.1258(8) Å，Z = 4，而CsNaNbOF5以正交空间群Pbcn（编号60）结晶，晶格常数a = 8.3155(7)，b = 13.3176(11)，c = 11.1314(9)，Z = 8。