Faculty of Chemistry, University of the Basque Country UPV/EHU, and Donostia International Physics Center, P.K. 1072, 20080 Donostia, Euskadi, Spain.
Phys Chem Chem Phys. 2011 Dec 7;13(45):20129-35. doi: 10.1039/c1cp21696a. Epub 2011 Sep 9.
The dissociation of diatomic molecules of the 14-electron isoelectronic series N(2), O(2)(2+), CO, CN(-) and NO(+) is examined using the Piris natural orbital functional. It is found that the method describes correctly the dissociation limit yielding an integer number of electrons on the dissociated atoms, in contrast to the fractional charges obtained when using the variational two-particle reduced density matrix method under the D, Q and G positivity necessary N-representability conditions. The chemistry of the considered systems is discussed in terms of their dipole moments, natural orbital occupations and bond orders as well as atomic Mulliken populations at the dissociation limit. The values obtained agree well with accurate multiconfigurational wave function based CASSCF results and the available experimental data.
使用 Piris 自然轨道函数研究了 14 电子等电子系列 N(2)、O(2)(2+)、CO、CN(-) 和 NO(+) 的双原子分子的离解。结果发现，该方法正确描述了离解极限，在离解原子上得到整数个电子，而与在 D、Q 和 G 正定性必要 N 可表示性条件下使用变分双粒子约化密度矩阵方法得到的分数电荷形成对比。根据它们的偶极矩、自然轨道占据和键序以及离解极限处的原子 Mulliken 布居，讨论了所考虑体系的化学性质。得到的值与基于精确多组态波函数的 CASSCF 结果和可用的实验数据吻合良好。
