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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Coming to Grips with N-H…N Bonds. 1. Distance Relationships and Electron Density at the Bond Critical Point
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Coming to Grips with N-H…N Bonds. 1. Distance Relationships and Electron Density at the Bond Critical Point

机译：带着N-H…N债券一触即发。 1.键临界点的距离关系和电子密度

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摘要

In an attempt to discover and analyze trends in distance relationships and properties at the bond critical point (BCP) in linear or near-linear N-H N hydrogen bonds, tne geometry of such bonds in a large number of suitable simple chemical species was optimized at the RHF/6-3lG~(**) level. The results for 67 of these are reported here; the geometry of 19 of them was optimized also at the MP2/6-3lG~(**) level. Correlations between the internuclear N…H, H…N, and N…N separations as well as between the NBCP and H~ BCP distances for these data sets and for different model functions are described in detail. The special case of symmetric N-H-N bonds is discussed; comparison with available experimental evidence shows that the correlation functions derived from the ab initio data have useful predictive value for crystallographic determinations involving short N-H-N bonds. Analysis of the correlation between the d(N-H) distance and the electron density P. at the BCP has shown that although acceptable d,p representations are obtained when Pc is fitted over the entire d(N-H) range by a single model function, significantly better fits result for both the 6-31G~(**) and the MP2/6-3IG~(**) set when two separate regression functions of the same type are used, one for the covalent and another for the H N bonds. The implications of these findings are discussed. The results of the correlation analysis of the curvatures #lambda#_i, the Laplacians Pc, and the kinetic energy densities at the BCP, based on the data presented in this paper, will be reported in a subsequent paper, together with some aspects of the energy of formation of the N-H…N bonds.
机译：为了发现和分析线性或接近线性NH N氢键中键临界点（BCP）的距离关系和性质的趋势，我们优化了许多合适的简单化学物种中此类键的几何构型。 RHF / 6-3lG〜（**）水平。其中67个结果报告在这里;在MP2 / 6-3lG〜（**）级别上，其中19个的几何形状也得到了优化。对于这些数据集和不同的模型函数，将详细描述核间距N…H，H…N和N…N之间的相关性，以及NBCP和H〜BCP距离之间的相关性。讨论了对称的N-H-N键的特殊情况;与现有实验证据的比较表明，从头算数据得出的相关函数对于涉及短N-H-N键的晶体学测定具有有用的预测价值。对BCP处d（NH）距离与电子密度P.之间的相关性的分析表明，尽管通过单个模型函数将Pc拟合在整个d（NH）范围内，尽管可以得到可接受的d，p表示，当使用两个相同类型的单独回归函数，一个用于共价键，另一个用于HN键时，对于6-31G〜（**）和MP2 / 6-3IG〜（**）集合的拟合结果更好。讨论了这些发现的含义。根据本文提供的数据，将在随后的论文中报告曲率＃lambda＃_i，拉普拉斯算子Pc和BCP处动能密度的相关分析结果，并将结合以下方面进行报告。 NH…N键的形成能。

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