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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Molecular electric moments and electric field gradients from X-ray diffraction data: model studies
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Molecular electric moments and electric field gradients from X-ray diffraction data: model studies

机译：X射线衍射数据的分子电矩和电场梯度：模型研究

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摘要

Model X-ray data sets, with and without the inclusion of experimental thermal motion parameters, have been computed via Fourier transformation of ab initio molecular electron densities for 12 different molecular crystals. These datasets were then analysed with three different multipole models of varying sophistication and, from the multipole functions, molecular dipole and second moments, as well as electric field gradients (EFG's), at each nuclear site were computed and compared with results obtained from the original ab initio wavefunctions. The results provide valuable insight into the reliability of these properties, extracted in the same way from experimental X-ray data. Not all molecular systems display identical trends, but a general pattern is discernible. Specifically, dipole moments are typically underestimated by a small but significant amount (~ 10-15%), the trace of the second moment tensor is well determined but overestimated by a few per cent and electric field gradients at protons are confirmed to be well within reach of a careful charge density analysis of X-ray diffraction data.
机译：通过对12种不同分子晶体的从头算分子电子密度进行傅里叶变换，计算了带有和不带有实验热运动参数的X射线模型数据集。然后，使用三种不同复杂程度的不同多极模型对这些数据集进行分析，并从多极函数中计算出每个核位置处的分子偶极矩和第二矩以及电场梯度（EFG），并将其与原始结果进行比较。从头算起波函数。从实验X射线数据中以相同的方式提取的结果为这些特性的可靠性提供了有价值的见解。并非所有分子系统都显示出相同的趋势，但是可以识别出一般模式。具体而言，偶极矩通常会被低估但很小（约10-15％），第二矩张量的迹线可以很好地确定，但被百分之几高估，并且质子上的电场梯度被确定在仔细进行X射线衍射数据的电荷密度分析。

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