Nonadiabatic Car-Parrinello Molecular Dynamics Studies of Photochemical Processes

光化学过程的非绝热 Car-Parrinello 分子动力学研究

• 批准号: 5397860
• 负责人: Professor Dr. Nikos L. Doltsinis
• 金额: --
• 依托单位: Institut für Festkörpertheorie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2003
• 资助国家: 德国
• 起止时间: 2002-12-31 至 2008-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5397860?language=en
• 关键词: Nonadiabatic; Car; Parrinello; Molecular; Dynamics

State-of-the-art as well as novel ab initio molecular dynamics (MD) techniques will be employed in order to study two photochemical phenomena of fundamental importance, namely excited state tautomerism in the DNA base guanine and photoisomerisation of azobenzene. A density functional restricted openshell Kohn-Sham method will be used to determine optimized geometries as weil as vibrational frequencies in the S, excited electronic state. Both harmonic and anharmonic vibrational spectra will be analysed for different tautomers in search of spectral 'fingerprints' making possible the assignment of experimental IR spectra. Excited state proton transfer (ESPT) interconverting keto and enol tautomers will be investigated by means of the recently developed nonadiabatic Car-Parrinello MD (na-CP-MD) method. This approach further allows studying radiationless decay of the S, electronically excited state to the So ground state. Effects of solvation on the relative stability of the different tautomers and on the barrier heights for ESPT shall be studied by CP-MD and its nonadiabatic extension using explicit water solvent molecules in a periodic system. Furthermore, such an approach allows studying solvent-mediated proton transfer pathways which might be very different from the ones observed in the gas phase. Cis-trans and trans-cis photoisomerisation of azobenzene shall be studied both in the gas phase and in solution using the na-CP-MD approach. Constraint dynamics simulations will be performed to compute the contraction force and its interplay with changes of the electronic structure during trans-cis isomerisation in order to uncover the mechanistic underlying recent atomic force microscopy (AFM) experiments.

国家的最先进的，以及新的从头算分子动力学（MD）技术将采用，以研究两个光化学现象的根本重要性，即激发态互变异构的DNA碱基鸟嘌呤和偶氮苯的光异构化。密度泛函限制的开壳层Kohn-Sham方法将用于确定优化的几何结构以及S1激发电子态的振动频率。谐波和非谐波振动光谱将分析不同的互变异构体的光谱“指纹”的搜索，使实验红外光谱的分配成为可能。利用新近发展的非绝热Car-Parrinello分子动力学（na-CP-MD）方法研究了激发态质子转移（ESPT）互变的酮和烯醇互变异构体。这种方法还允许研究S1电子激发态到S 0基态的无辐射衰减。溶剂化对不同互变异构体的相对稳定性和对ESPT的势垒高度的影响应通过CP-MD及其非绝热扩展使用明确的水溶剂分子在周期性系统中进行研究。此外，这种方法允许研究溶剂介导的质子转移途径，这可能与气相中观察到的质子转移途径非常不同。应使用na-CP-MD方法研究气相和溶液中偶氮苯的顺-反和反-顺光异构化。约束动力学模拟将进行计算的收缩力和它的相互作用，在反式-顺式异构化的电子结构的变化，以揭示最近的原子力显微镜（AFM）实验的机制。