Electronic coupling matrix elements from charge constrained density functional theory calculations using a plane wave basis set.
Electronic coupling matrix elements from charge constrained density functional theory calculations using a plane wave basis set.
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DOI：
10.1063/1.3507878
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发表时间：
2010-12
期刊：
影响因子：
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通讯作者：
H. Oberhofer;J. Blumberger
中科院分区：
文献类型：
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作者：
H. Oberhofer;J. Blumberger
我们提出了一种平面波基组实现，用于在约束密度泛函理论（CDFT）框架内计算电子转移反应的电子耦合矩阵元素。遵循 Wu 和 Van Voorhis 的工作 [J.化学。物理。 125, 164105 (2006)]，非绝热波函数通过 CDFT 计算获得的 Kohn-Sham 行列式进行近似，并通过有效的积分方案计算耦合矩阵元素。我们对小系统中分子间电子转移的结果与基于广义 Mulliken-Hush 理论的高级从头计算以及之前的局部基组 CDFT 计算非常一致。热波动对耦合矩阵元素的影响被证明适用于四硫富瓦烯-二醌 (Q-TTF-Q(-)) 阴离子中的分子内电子转移。沿着基于密度泛函的分子动力学轨迹对电子耦合进行采样，我们发现热波动，特别是分子的缓慢弯曲运动，可以导致瞬时电子转移速率的变化超过一个数量级。热平均值 ()(1/2)=6.7 mH 明显高于最小能量结构获得的值 |H(ab)|=3.8 mH。虽然 CDFT 与广义梯度近似 (GGA) 泛函相结合很好地描述了所研究系统中的分子间电子转移，但 Q-TTF-Q(-) 需要精确交换才能获得与实验一致的耦合矩阵元素 (3.9 mH)。所提出的实现开辟了计算扩展系统的电子耦合矩阵元素的可能性，其中供体、受体和环境在量子力学（QM）水平上进行处理。
We present a plane wave basis set implementation for the calculation of electronic coupling matrix elements of electron transfer reactions within the framework of constrained density functional theory (CDFT). Following the work of Wu and Van Voorhis [J. Chem. Phys. 125, 164105 (2006)], the diabatic wavefunctions are approximated by the Kohn-Sham determinants obtained from CDFT calculations, and the coupling matrix element calculated by an efficient integration scheme. Our results for intermolecular electron transfer in small systems agree very well with high-level ab initio calculations based on generalized Mulliken-Hush theory, and with previous local basis set CDFT calculations. The effect of thermal fluctuations on the coupling matrix element is demonstrated for intramolecular electron transfer in the tetrathiafulvalene-diquinone (Q-TTF-Q(-)) anion. Sampling the electronic coupling along density functional based molecular dynamics trajectories, we find that thermal fluctuations, in particular the slow bending motion of the molecule, can lead to changes in the instantaneous electron transfer rate by more than an order of magnitude. The thermal average, ()(1/2)=6.7 mH, is significantly higher than the value obtained for the minimum energy structure, |H(ab)|=3.8 mH. While CDFT in combination with generalized gradient approximation (GGA) functionals describes the intermolecular electron transfer in the studied systems well, exact exchange is required for Q-TTF-Q(-) in order to obtain coupling matrix elements in agreement with experiment (3.9 mH). The implementation presented opens up the possibility to compute electronic coupling matrix elements for extended systems where donor, acceptor, and the environment are treated at the quantum mechanical (QM) level.