Curve crossing in a manifold of coupled electronic states: direct quantum dynamics simulations of formamide,Faraday Discussions

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Curve crossing in a manifold of coupled electronic states: direct quantum dynamics simulations of formamide
Faraday Discussions ( IF 3.3 ) Pub Date : 2018-05-16 , DOI: 10.1039/c8fd00090e
K. Eryn Spinlove _{1,

2,

3,

4,

5} , Gareth W. Richings _{1,

4,

6,

7} , Michael A. Robb _{1,

3,

4,

8} , Graham A. Worth _{1,

2,

3,

4}

Affiliation

Quantum dynamics simulations are an important tool to evaluate molecular behaviour including the, often key, quantum nature of the system. In this paper we present an algorithm that is able to simulate the time evolution of a molecule after photo-excitation into a manifold of states. The direct dynamics variational multi-configurational Gaussian (DD-vMCG) method circumvents the computational bottleneck problems of traditional grid-based methods by computing the potential energy functions on-the-fly, i.e. only where required. Unlike other commonly used direct dynamics methods, DD-vMCG is fully quantum mechanical. Here, the method is combined with a novel on-the-fly diabatisation scheme to simulate the short-time dynamics of the key molecule formamide and its acid analogue formimidic acid. This is a challenging test system due to the nature and large number of excited states, and eight coupled states are included in the calculations. It is shown that the method is able to provide unbiased information on the product channels open after excitation at different energies and demonstrates the potential to be a practical scheme, limited mainly by the quality of the quantum chemistry used to describe the excited states.

中文翻译：

耦合电子态流形中的曲线交叉：甲酰胺的直接量子动力学模拟

量子动力学仿真是评估分子行为的重要工具，其中分子行为通常包括系统的关键量子性质。在本文中，我们提出了一种算法，该算法能够模拟光激发成多种状态后分子的时间演化。直接动力学变分多构型高斯（DD-VMCG）一种方法绕过了通过计算势能函数上即时，传统的基于网格的方法中的计算瓶颈问题即仅在需要的地方。与其他常用的直接动力学方法不同，DD-vMCG是完全量子力学的。在这里，该方法与一种新型的动态绝热方案相结合，以模拟关键分子甲酰胺及其酸类似物甲酰亚胺酸的短时动力学。由于性质和大量的激发态，这是一个具有挑战性的测试系统，并且在计算中包括八个耦合态。结果表明，该方法能够在以不同能量激发后打开的产物通道上提供无偏信息，并证明了它是一种可行的方案，主要受用于描述激发态的量子化学质量的限制。

更新日期：2018-12-21

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