Vladimirov Egor, Ivanova Anela, Rösch Notker
Department Chemie, Theoretische Chemie, Technische Universität München, 85748 Garching, Germany.
J Chem Phys. 2008 Nov 21;129(19):194515. doi: 10.1063/1.3013456.
The solvent contribution lambda(s) to the reorganization energy of electron transfer can be estimated from averages of the potential energy gaps between neutral-pair and ion-pair states over an ensemble of structures generated from molecular dynamics simulations. Invoking a Marcus-type two-sphere model for charge separation and recombination in an aqueous environment, we explored the effect of a polarizable force field and noted a strong reduction of lambda(s) (by approximately 45%) compared to the corresponding value obtained with a standard nonpolarizable force field. Both types of force fields yield lambda(s) values that in agreement with the Marcus theory, vary strictly linearly with the inverse of the donor-acceptor distance; the corresponding slopes translate into appropriate effective optical dielectric constants, epsilon(infinity) approximately 1.0+/-0.2 for a nonpolarizable and epsilon(infinity) approximately 1.7+/-0.4 for a polarizable force field. The reduction in the solvent reorganization energy due to a polarizable force field translates into a scaling factor that is essentially independent of the donor-acceptor distance. The corresponding effective optical dielectric constant, epsilon(infinity) approximately 1.80, is in excellent agreement with experiment for water.
电子转移重组能的溶剂贡献λ(s)可通过分子动力学模拟生成的一组结构上中性对和离子对状态之间势能间隙的平均值来估算。在水相中电荷分离和复合的过程中，我们采用Marcus型双球模型，研究了可极化力场的影响，并注意到与标准非极化力场得到的相应值相比，λ(s)有显著降低（约45%）。两种力场得到的λ(s)值均符合Marcus理论，且与供体-受体距离的倒数严格呈线性变化；相应的斜率转化为适当的有效光学介电常数，对于非极化力场，ε(∞)约为1.0±0.2，对于可极化力场，ε(∞)约为1.7±0.4。由于可极化力场导致的溶剂重组能降低转化为一个基本上与供体-受体距离无关的比例因子。相应的有效光学介电常数ε(∞)约为1.80，与水的实验值非常吻合。
