Fully Polarizable QM/Fluctuating Charge Approach to Two-Photon Absorption of Aqueous Solutions
Fully Polarizable QM/Fluctuating Charge Approach to Two-Photon Absorption of Aqueous Solutions
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DOI：
10.1021/acs.jctc.9b00305
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发表时间：
2019-07-01
影响因子：
5.5
通讯作者：
Frediani, Luca
中科院分区：
文献类型：
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作者：
Di Remigio, Roberto;Giovannini, Tommaso;Frediani, Luca
为了计算双光子吸收截面，我们将量子/经典极化波动电荷模型推广到二次响应函数的单余量的计算。借助于量子/经典极化耦合的变分形式，我们能够利用基于原子轨道的准能量形式来推导响应方程中的附加耦合项。我们的形式可以推广到任意阶响应函数及其残数的计算。该方法已应用于罗丹明6G(R6G)在水溶液中的单光子和双光子光谱这一具有挑战性的问题。从连续介质(QM/PCM)到两种QM/MM模型(非极化QM/TIP3P和可极化QM/FQ)，用三种不同的方法分析了溶剂对R6G水溶液中单光子和双光子光谱的影响。QM/TIP3P和QM/FQ模拟的OPA和TPA光谱都表明，离散水溶剂分子的加入对于提高理论和实验的一致性是必不可少的。QM/FQ已被证明与实验的一致性最好。
We present the extension of the quantum/classical polarizable fluctuating charge model to the calculation of single residues of quadratic response functions, as required for the computational modeling of two-photon absorption cross sections. By virtue of a variational formulation of the quantum/classical polarizable coupling, we are able to exploit an atomic orbital-based quasienergy formalism to derive the additional coupling terms in the response equations. Our formalism can be extended to the calculation of arbitrary order response functions and their residues. The approach has been applied to the challenging problem of one- and two-photon spectra of rhodamine 6G (R6G) in aqueous solution. Solvent effects on one- and two-photon spectra of R6G in aqueous solution have been analyzed by considering three different approaches, from a continuum (QM/PCM) to two QM/MM models (nonpolarizable QM/TIP3P and polarizable QM/FQ). Both QM/TIP3P and QM/FQ simulated OPA and TPA spectra show that the inclusion of discrete water solvent molecules is essential to increase the agreement between theory and experiment. QM/FQ has been shown to give the best agreement with experiments.