Dissociation of diatomic molecules and the exact-exchange Kohn-Sham potential: the case of LiF
Dissociation of diatomic molecules and the exact-exchange Kohn-Sham potential: the case of LiF
复制标题
双原子分子的解离和精确交换 Kohn-Sham 势：LiF 的情况
DOI：
--
复制
发表时间：
2011
期刊：
影响因子：
--
通讯作者：
L. Kronik
中科院分区：
文献类型：
--
作者：
A. Makmal;S. Kuemmel;L. Kronik
我们研究了精确交换（EXX）Kohn-Sham势在解决分数分子解离问题中的作用。这是通过对LiF分子的示例性情况进行EXX计算来实现的。我们表明，通过选择最低能量的电子配置为每个原子间的距离，一个定性正确的结合能曲线，反映整数解离，得到。令人惊讶的是，对于LiF来说，这是以违反Aufbau原则为代价的，这是我们详细讨论的现象。此外，我们数值证实，在双原子分子的EXX势，原子的潜力之一是由一个常数，而另一个不是移动，这取决于最高占据的分子轨道是本地化。这改变了每个原子能量的相对位置，并通过防止虚假电荷转移来强制执行整数配置。原子间的距离越大，常数位移的大小在数值上变得越来越不稳定，反映了原子之间越来越不存在耦合。
We examine the role of the exact-exchange (EXX) Kohn-Sham potential in curing the problem of fractional molecular dissociation. This is achieved by performing EXX calculations for the illustrative case of the LiF molecule. We show that by choosing the lowest-energy electronic configuration for each interatomic distance, a qualitatively correct binding energy curve, reflecting integer dissociation, is obtained. Surprisingly, for LiF this comes at the cost of violating the Aufbau principle, a phenomenon we discuss at length. Furthermore, we numerically confirm that in the EXX potential of the diatomic molecule, one of the atomic potentials is shifted by a constant while the other one is not, depending on where the highest occupied molecular orbital is localized. This changes the relative positions of the energies of each atom and enforces the integer configuration by preventing spurious charge transfer. The size of the constant shift becomes increasingly unstable numerically the larger the interatomic separation is, reflecting the increasing absence of coupling between the atoms.