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首页> 外文期刊>Chemistry: A European journal >Unravelling Local Atomic Order of the Anionic Sublattice in M(Al1-xGax)(4) with M = Sr and Ba by Using NMR Spectroscopy and Quantum Mechanical Modelling
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Unravelling Local Atomic Order of the Anionic Sublattice in M(Al1-xGax)(4) with M = Sr and Ba by Using NMR Spectroscopy and Quantum Mechanical Modelling

机译：通过使用核磁共振波谱和量子力学建模，对M = Sr和Ba的M（Al1-xGax）（4）中阴离子亚晶格的局部原子序进行分解

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摘要

The quasibinary section of the intermetallic phases MAl4 and MGa4 with M = Sr and Ba have been characterised by means of X-ray diffraction (XRD) studies and differential thermal analysis. The binary phases show complete miscibility and form solid solutions M(Al1-xGax)(4) with M = Sr and Ba. These structures crystallise in the BaAl4 structure type with four- and five-bonded Al and/or Ga atoms (denoted as Al(4b), Al(5b), Ga(4b), and Ga(5b), respectively) that form a polyanionic Al/Ga sublattice. Solid state Al-27 NMR spectroscopic analysis and quantum mechanical (QM) calculations were applied to study the bonding of the Al centres and the influence of Al/Ga substitution, especially in the regimes with low degrees of substitution. M(Al1-xGax)(4) with M = Sr and Ba and 0.925 < x < 0.975 can be described as a matrix of the binary majority compound in which a low amount of the Ga atoms has been substituted by Al atoms. In good agreement with the QM calculations, Al-27 NMR investigations and single crystal XRD studies prove a preferred occupancy of Al(4b) for these substitution regimes. Furthermore, two different local Al environments were found, namely isolated Al(4b1) atoms and Al(4b2), due to the formation of Al(4b)-Al(4b) pairs besides isolated Al(4b) atoms within the polyanionic sublattice. QM calculations of the electric field gradient (EFG) using superlattice structures under periodic boundary conditions are in good agreement with the NMR spectroscopic results.
机译：金属间相MAl4和MGa4的准二元截面（M = Sr和Ba）已通过X射线衍射（XRD）研究和差热分析进行了表征。二元相显示出完全的混溶性，并形成固溶体M（Al1-xGax）（4），其中M = Sr和Ba。这些结构以四键和五键的Al和/或Ga原子（分别表示为Al（4b），Al（5b），Ga（4b）和Ga（5b））以BaAl4结构类型结晶。聚阴离子Al / Ga亚晶格。固态Al-27 NMR光谱分析和量子力学（QM）计算用于研究Al中心的键合以及Al / Ga取代的影响，特别是在取代度较低的体系中。具有M = Sr和Ba并且0.925

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