Department of Chemistry and Material Science, School of Chemical Engineering, Aalto University Kemistintie 1, 02150 Espoo, Finland.
Phys Chem Chem Phys. 2020 Nov 18;22(44):25833-25840. doi: 10.1039/d0cp04508j.
A protocol for the accurate computation of electron transfer (ET) potentials from ab initio and density functional theory (DFT) calculations is described. The method relies on experimental pKa values, which can be measured accurately, to compute a computational setup dependent effective absolute potential. The effective absolute potentials calculated using this protocol display strong variations between the different computational setups and deviate in several cases significantly from the "generally accepted" value of 4.28 V. The most accurate estimate, obtained from CCSD(T)/aug-ccpvqz, indicates an absolute potential of 4.14 V for the normal hydrogen electrode (nhe) in water. Using the effective absolute potential in combination with CCSD(T) and a moderately sized basis, we are able to predict ET potentials accurately for a test set of small organic molecules (σ = 0.13 V). Similarly we find the effective absolute potential method to perform equally good or better for all considered DFT functionals compared to using one of the literature values for the absolute potential. For, M06-2X, which comprises the most accurate DFT method, standard deviation of 0.18 V is obtained. This improved performance is a result of using the most appropriate effective absolute potential for a given method.
描述了一种从从头计算和密度泛函理论 (DFT) 计算中准确计算电子转移 (ET) 势的协议。该方法依赖于实验 pKa 值，这些值可以准确测量，从而计算出与计算设置相关的有效绝对电势。使用该协议计算的有效绝对电势在不同的计算设置之间显示出强烈的变化，并且在几种情况下与通常接受的值 4.28 V 显著偏离。最准确的估计值是从 CCSD(T)/aug-ccpvqz 获得的，对于水中的标准氢电极 (nhe)，绝对电势为 4.14 V。使用有效绝对电势与 CCSD(T) 和中等大小的基组相结合，我们能够准确预测一组小有机分子的 ET 势（σ=0.13 V）。同样，与使用绝对电势的文献值之一相比，我们发现有效绝对电势方法对于所有考虑的 DFT 函数都表现同样好或更好。对于包含最准确 DFT 方法的 M06-2X，得到了 0.18 V 的标准偏差。这种改进的性能是因为为给定的方法使用了最合适的有效绝对电势。
