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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ab Initio Calculation of ~(81)Br Nuclear Quadrupole Resonance Transition Frequencies for Brominated Aromatics (Flame Retardants)
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Ab Initio Calculation of ~(81)Br Nuclear Quadrupole Resonance Transition Frequencies for Brominated Aromatics (Flame Retardants)

机译：溴代芳烃（阻燃剂）的〜（81）Br核四极共振跃迁频率从头算。

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摘要

Brominated aromatics, used extensively as flame retardants, have been studied with ~(81)Br nuclear quadrupole resonance (NQR) spectroscopy. NQR requires lengthy frequency searches because ~(81)Br NQR transition frequencies in brominated aromatics are spread over a wide (40 MHz) range. We investigate the ability of ab initio calculations to narrow this search range by predicting ~(81)Br NQR transition frequencies for a series of brominated aromatics, using restricted Hartree-Fock (RHF) and Becke's three-parameter Lee-Yang-Parr density functional theory hybrid method (B3LYP). Basis sets used are of double and triple-#xi# quality with varying degrees of polarization included on bromine. Geometries are the isolated molecules, with coordinates optimized for lowest energy. The results of calculations for nine simple brominated aromatics are fit against experimental frequencies and the fit is subsequently used to predict frequencies of larger, two-ring brominated aromatics (one is sold commercially as a flame retardant). Comparison to experiment shows the accuracy of this approach to be approximately 5 MHz, reflecting a significant, 8-fold decrease in the spectral range to be searched by experiment.
机译：溴化芳烃广泛用作阻燃剂，已通过〜（81）Br核四极共振（NQR）光谱进行了研究。 NQR需要冗长的频率搜索，因为溴化芳烃中的〜（81）Br NQR跃迁频率分布在很宽的（40 MHz）范围内。我们通过使用受限的Hartree-Fock（RHF）和Becke的三参数Lee-Yang-Parr密度泛函来预测一系列溴化芳族化合物的〜（81）Br NQR跃迁频率，来研究从头算计算来缩小此搜索范围的能力。理论混合法（B3LYP）。所使用的基组具有双重和三重质量，溴中包含不同的极化度。几何形状是孤立的分子，其坐标针对最低能量进行了优化。九种简单溴化芳族化合物的计算结果与实验频率相符，该拟合值随后用于预测较大的二环溴化芳族化合物的频率（一种以阻燃剂形式出售）。与实验的比较表明，该方法的精度约为5 MHz，反映出要搜索的光谱范围显着下降了8倍。

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