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首页> 外文期刊>The Journal of Chemical Physics >Locat and semiEocal density functional computations for crystals of 1-aikyl-3-methyl-imidazoIium salts
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Locat and semiEocal density functional computations for crystals of 1-aikyl-3-methyl-imidazoIium salts

机译：1-烷基-3-甲基咪唑鎓盐晶体的Locat和SemiEocal密度泛函计算

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摘要

The accuracy and reliability of popular density functional approximations for the compounds giving origin to room temperature ionic liquids have been assessed by computing the T=0 K crystal structure of several l-alkyl-3-methyl-imidazolium salts.Two prototypical exchange-correlation approximations have been considered,i.e.,the local density approximation(LDA)and one gradient corrected scheme [PBE-GGA,Phys.Rev.Lett.77,3865(1996)].Comparison with low-temperature x-ray diffraction data shows that the equilibrium volume predicted by either approximations is affected by large errors,nearly equal in magnitude(-10%),and of opposite sign.In both cases the error can be traced to a poor description of the intermolecular interactions,while the intramolecular structure is fairly well reproduced by LDA and PBE-GGA.The PBE-GGA optimization of atomic positions within the experimental unit cell provides results in good agreement with the x-ray structure.The correct system volume can also be restored by supplementing PBE-GGA with empirical dispersion terms reproducing the r~(-6)attractive tail of the van der Waals interactions.
机译：通过计算几种l-烷基-3-甲基咪唑鎓盐的T = 0 K晶体结构，已评估了源自室温离子液体的化合物的流行密度泛函近似的准确性和可靠性。两种典型的交换相关近似已经考虑了局部密度近似（LDA）和一种梯度校正方案[PBE-GGA，Phys.Rev.Lett.77,3865（1996）]。与低温x射线衍射数据的比较表明任一近似值所预测的平衡体积都受到较大误差的影响，该误差的大小几乎相等（-10％），并且符号相反。在两种情况下，误差都可以归因于对分子间相互作用的不良描述，而分子内结构相当由LDA和PBE-GGA很好地复制.PBE-GGA对实验晶胞内原子位置的优化提供了与x射线结构良好吻合的结果。还可以恢复正确的系统体积b y用经验分散项补充PBE-GGA，再现范德华相互作用的r〜（-6）吸引尾。

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