Unpaired electrons at the second-order reduced density matrix level: Covalent bonding, and coulomb and fermi correlations in closed shell systems
Unpaired electrons at the second-order reduced density matrix level: Covalent bonding, and coulomb and fermi correlations in closed shell systems
复制标题
二阶约化密度矩阵水平的不成对电子：闭壳系统中的共价键合以及库仑和费米相关性
DOI：
10.1002/qua.24399
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发表时间：
2013
影响因子：
2.2
通讯作者：
Katerina Kyriakidou
中科院分区：
文献类型：
--
作者：
P. Karafiloglou;Katerina Kyriakidou
通常闭合壳层系统原子轨道上的单电子布居在(自旋)二阶约化密度矩阵水平上分裂为未成对的和成对的。轨道中未配对的电子被定义为“在同一空间轨道中同时出现一个电子和一个自旋相反的电子空穴”，为简单起见，称为“电子”。给定轨道上的电子布居揭示了库仑关联是否以及在多大程度上是有利的，因此，该轨道与系统其余轨道之间的化学键是整体有利的还是不利的。两个靶轨道上两个电子的相互作用揭示了这些轨道之间共价键的性质(有利或不利)和强度，这在电子的概念和传统的价键(VB)理论之间建立了一座桥梁。两个轨道之间的有利/不利成键的特征是两个相反自旋的电子的正/负(库仑)关联，或者是两个平行自旋电子的负/正(费米)关联。定义了无自旋指数，建立了化学键的电子观点与著名的双电子库仑和费米关联之间的关系。根据有物理意义的自然轨道，对乙烯、己三烯、苯、吡咯、甲胺和氨分子进行了基准计算。在正交法和非正交法的框架下得到的结果提供了相同的概念图，与基本的化学知识和VB理论非常一致。弗吉尼亚州2013年威利
The usual one-electron populations in atomic orbitals of closed shell systems are split into unpaired and paired at the (spindependent) second-order reduced density matrix level. The unpaired electron in an orbital is defined as the ‘‘simultaneous occurrence of an electron and an electron hole of opposite spins in the same spatial orbital,’’ which for simplicity is called ‘‘electropon.’’ The electropon population in a given orbital reveals whether and to what degree the Coulomb correlations, and hence, the chemical bonding between this orbital and the remaining orbitals of the system are globally favorable or unfavorable. The interaction of two electropons in two target orbitals reveals the quality (favorable or unfavorable) and the strength of the covalent bonding between these orbitals; this establish a bridge between the notion of ‘ electrons’’ and the traditional covalent structure of valence-bond (VB) theory. Favorable/unfavorable bonding between two orbitals is characterized by the positive/negative (Coulomb) correlation of two electropons of opposite spins, or alternatively, by the negative/positive (Fermi) correlation of two parallel spin electropons. A spin-free index is defined, and the relationship between the electropon viewpoint for chemical bonding and the well-known two-electron Coulomb and Fermi correlations is established. Benchmark calculations are achieved for ethylene, hexatriene, benzene, pyrrole, methylamine, and ammonia molecules on the basis of physically meaningful natural orbitals. The results, obtained in the framework of both orthogonal and nonorthogonal population analysis methods, provide the same conceptual pictures, which are in very good agreement with elementary chemical knowledge and VB theory. V C 2013 Wiley