Experimental dynamic electron densities of multipole models at different temperatures.
Experimental dynamic electron densities of multipole models at different temperatures.
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不同温度下多极模型的实验动态电子密度。
DOI：
10.1107/s0108767312029005
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
S. van Smaalen
中科院分区：
文献类型：
--
作者：
S. Mondal;S. J. Prathapa;S. van Smaalen
结果表明，采用快速傅里叶变换的方法，通过精确计算的结构因子的傅里叶逆变换，可以计算出结构模型对应的动态电子密度。在直接空间中分辨率优于 0.04 Å 时获得了无系列终止效应的图，对应于倒易空间中分辨率大于 6 Å(-1) 的情况。通过对从科学文献中获得的 X 射线衍射数据进行细化，确定了不同温度下 α-甘氨酸和 D,L-丝氨酸的多极 (MP) 模型。动态电子密度的成功构建通过其拓扑特性得到证明，拓扑特性表明了基于相应静态电子密度预期位置的局部最大值和键临界点（BCP），而尚未发现非原子最大值。动态电子密度中接近原子最大值的密度值比静态电子密度小得多。静态和低温（~20 K）动态电子密度图在低密度区域中被发现惊人地相似。特别是在 BCP 处，∼20 K 动态密度图的值仅略小于相应静态密度图的值。这些零点振动的主要影响是密度二阶导数的修改，这对于极性 C-O 键 BCP 处的值最为明显。然而，动态 MP 电子密度为相应静态电子密度的 BCP 处的拓扑特性提供了合理精度的估计。静态和动态电子密度之间的差异随着温度的升高而增大。这些差异可能提供有关温度依赖性分子或固态特性（例如化学稳定性和反应性）的信息。在密度更低的区域，如氢键，静态和动态电子密度在所考虑的整个温度范围内 (20-298 K) 具有相似的外观，在所有温度下静态和动态电子密度的 BCP 处提供相似的密度及其拉普拉斯值。
It is shown that the dynamic electron density corresponding to a structure model can be computed by inverse Fourier transform of accurately calculated structure factors, employing the method of fast Fourier transform. Maps free of series-termination effects are obtained for resolutions better than 0.04 Å in direct space, corresponding to resolutions larger than 6 Å(-1) in reciprocal space. Multipole (MP) models of α-glycine and D,L-serine at different temperatures have been determined by refinement against X-ray diffraction data obtained from the scientific literature. The successful construction of dynamic electron densities is demonstrated by their topological properties, which indicate local maxima and bond-critical points (BCPs) at positions expected on the basis of the corresponding static electron densities, while non-atomic maxima have not been found. Density values near atomic maxima are much smaller in dynamic than in static electron densities. Static and low-temperature (∼20 K) dynamic electron-density maps are found to be surprisingly similar in the low-density regions. Especially at BCPs, values of the ∼20 K dynamic density maps are only slightly smaller than values of the corresponding static density maps. The major effect of these zero-point vibrations is a modification of the second derivatives of the density, which is most pronounced for values at the BCPs of polar C-O bonds. Nevertheless, dynamic MP electron densities provide an estimate of reasonable accuracy for the topological properties at BCPs of the corresponding static electron densities. The difference between static and dynamic electron densities increases with increasing temperature. These differences might provide information on temperature-dependent molecular or solid-state properties like chemical stability and reactivity. In regions of still lower densities, like in hydrogen bonds, static and dynamic electron densities have similar appearances within the complete range of temperatures that have been considered (20-298 K), providing similar values of both the density and its Laplacian at BCPs in static and dynamic electron densities at all temperatures.