Carmona-Espíndola Javier, Flores Anaid, Ireta Joel, Gázquez José L
Departamento de Química, CONAHCYT-Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, Ciudad de México 09340, Mexico.
Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, Ciudad de México 09340, Mexico.
J Chem Phys. 2024 Dec 21;161(23). doi: 10.1063/5.0235534.
The charge-transfer energy contribution is one of the most controversial components of the total interaction energy. Commonly, the energy associate to a charge-transfer process depends on population analysis. Therefore, the results further depend on how the population analysis is defined, and certainly, the results may be arbitrary. Moreover, another important feature of the current methods is the basis sets dependency. The results of methodologies that depend on orbital-based population analyses tend to have a strong dependency on the size of the basis set utilized. This basis set dependency is eliminated by using spatial partitioning population analyses. However, these methodologies still rely on the arbitrary choice of how to divide the space. In this work, we study the use of the molecular dipole moment as a reference to describe the charge transfer-free system, i.e., a system in which the charge-transfer process is avoided. We use the recently developed constrained dipole moment density functional theory methodology to constrain the dipole moment of several systems according to reference values. These dipole moment references do not present charge transfer nor polarization contributions. In this manner, we have calculated the charge-transfer energy contributions and the total interaction energies of 13 non-covalent complexes. In addition, we determined two long range charge-transfer excitations considering the dipole moment as a reference. The calculated charge-transfer energy contributions and excitation energies are in a very good agreement with the fragment-based Hirshfeld methodology. Nevertheless, the constrained dipole moments results do not depend on population analysis. Moreover, the method is robust with respect to the strength of the charge transfer and the basis set size.
电荷转移能量贡献是总相互作用能中最具争议的组成部分之一。通常，与电荷转移过程相关的能量取决于布居分析。因此，结果进一步取决于布居分析是如何定义的，当然，结果可能是任意的。此外，当前方法的另一个重要特征是对基组的依赖性。依赖于基于轨道的布居分析的方法结果往往对所使用基组的大小有很强的依赖性。通过使用空间划分布居分析消除了这种基组依赖性。然而，这些方法仍然依赖于如何划分空间的任意选择。在这项工作中，我们研究使用分子偶极矩作为参考来描述无电荷转移的体系，即避免电荷转移过程的体系。我们使用最近开发的约束偶极矩密度泛函理论方法，根据参考值来约束几个体系的偶极矩。这些偶极矩参考值不存在电荷转移和极化贡献。通过这种方式，我们计算了13个非共价配合物的电荷转移能量贡献和总相互作用能。此外，我们以偶极矩为参考确定了两种长程电荷转移激发。计算得到的电荷转移能量贡献和激发能与基于片段的赫希菲尔德方法非常吻合。然而，约束偶极矩的结果不依赖于布居分析。此外，该方法对于电荷转移强度和基组大小具有鲁棒性。
