Sablon Nick, De Proft Frank, Geerlings Paul, Tozer David J
Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050, Brussels, Belgium.
Phys Chem Chem Phys. 2007 Nov 28;9(44):5880-4. doi: 10.1039/b711428a. Epub 2007 Sep 24.
A simple method was recently proposed [D. J. Tozer and F. De Proft, J. Chem. Phys., 2007, 127, 034108] for performing explicit density functional theory (DFT) calculations on temporary anions. The excess electron in the anion is bound by a potential wall, the position of which is determined by a single parameter lambda, chosen to reproduce an approximate, theoretical negative electron affinity in the corresponding neutral. In the present study, the system-dependence of lambda and the sensitivity of the negative affinities to this parameter are investigated for 34 organic molecules. The results demonstrate that the system-dependent lambda values can be replaced by a global, average value, with minimal effect on the affinities. It follows that the orbitals, electron density, and other properties of a temporary anion can be determined from a single DFT calculation on that anion, using a large, diffuse basis set. As an illustration, singly occupied molecular orbitals and spin densities are determined for the anions of guanine and adenine nucleobases. Despite the use of a diffuse basis set, the method yields quantities that are localised in the molecular framework, associated with vertical electron affinities of -1.2 eV and -0.8 eV, respectively.
最近有人提出了一种简单的方法[D. J. 托泽尔和F. 德普罗夫特，《化学物理杂志》，2007年，第127卷，034108]，用于对临时阴离子进行显式密度泛函理论（DFT）计算。阴离子中的多余电子被一个势垒束缚，势垒的位置由单个参数λ确定，该参数被选择用来重现相应中性分子中近似的理论负电子亲和能。在本研究中，针对34种有机分子研究了λ的系统依赖性以及负亲和能对该参数的敏感性。结果表明，与系统相关的λ值可以用一个全局平均值代替，而对亲和能的影响最小。由此可知，临时阴离子的轨道、电子密度和其他性质可以通过对该阴离子进行单次DFT计算来确定，使用大的弥散基组。作为一个示例，确定了鸟嘌呤和腺嘌呤核碱基阴离子的单占据分子轨道和自旋密度。尽管使用了弥散基组，但该方法得到的量在分子框架中是局域化的，分别对应垂直电子亲和能为-1.2 eV和-0.8 eV。
