27Al NMR Chemical Shifts in Oxide Crystals: A First-Principles Study

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• 作者：Minseok Choi*^† ; ; Katsuyuki Matsunaga^† ; ^‡ ; ; Fumiyasu Oba^† ; ; Isao Tanaka*^† ; ^‡ ;
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：March 5, 2009
• 年：2009
• 卷：113
• 期：9
• 页码：3869-3873
• 全文大小：185K
• 年卷期：v.113,no.9(March 5, 2009)
• ISSN：1932-7455

文摘

In the framework of density functional theory using periodic boundary conditions, ²⁷Al nuclear magnetic resonance (NMR) parameters of 20 aluminum sites in 12 aluminum-containing crystalline oxides, i.e., Al₂O₃, LiAlO₂, SiAl₂O₅, MgAl₂O₄, YAlO₃, AlVO₄, and their polymorphs, are investigated. The present method excellently reproduces the ²⁷Al NMR parameters and the well-known empirical correlation of the isotropic chemical shifts, δ_iso, of ²⁷Al nuclei with its number of coordinating oxygen atoms, i.e., coordination number. Through systematic calculations, we demonstrate that the mean Al−O bond order, Q_Al−O, can be a better parameter to correlate with ²⁷Al δ_iso than merely averaged bond length or the coordination number. The relationship between δ_iso and Q_Al−O is also found to be valid for α-Al₂O₃ under hydrostatic pressures in which the coordination number is unchanged from six.