热激发芘（C $_{16}$ H $_{10}$）的非谐红外光谱：基于DFT的GVPT2与AnharmonicCaOs和近似DFT分子动力学与DemonNano的结合
Anharmonic Infrared Spectra of Thermally Excited Pyrene(C$_{16}$H$_{10}$): the combined view of DFT-based GVPT2 with AnharmonicCaOs and approximate DFT molecular dynamics with DemonNano
摘要：
天文环境中芳香族红外带（AIBs）的研究，揭示了非谐性对高温多环芳烃（PAHs）及其相关物种在孤立条件下红外光谱的影响。即将到来的詹姆斯·韦伯太空望远镜将揭示AIB光谱中前所未有的空间和光谱细节;因此，现在有必要取得重大进展来模拟多环芳烃的红外发射，它们的假定载体，具有足够的细节来利用AIB的信息内容。这需要在这些模型中包括非调和性，并且系统地为所有物种包括在内，这需要在准确性和效率之间做出艰难的妥协。我们进行了一个基准研究，比较两种方法在计算非谐谱的性能，比较它们与现有的实验数据。一个是全量子方法，AnharmoniCaOs，依赖于从头算潜力，和其他依赖于分子动力学模拟使用密度泛函为基础的紧结合势。第一个被发现是非常准确和详细的，但它变得非常昂贵的计算增加温度;第二个是更快，可以用于任意高的温度，但不太准确。尽管如此，它的结果可以用来模拟孤立带随温度的演化。我们提出了一个新的配方来模拟非谐AIB发射使用最小的假设的一般行为的带的位置和宽度与温度，这可以定义为一个小数目的经验参数。模型的准确性将主要取决于这些经验参数，随着更好的估计逐渐出现，模型结果将逐步得到改进。
英文摘要：
The study of the Aromatic Infrared Bands (AIBs) in astronomical environments has opened interesting spectroscopic questions on the effect of anharmonicity on the infrared (IR) spectrum of hot polycyclic aromatic hydrocarbons (PAHs) and related species in isolated conditions. The forthcoming James Webb Space Telescope will unveil unprecedented spatial and spectral details in the AIB spectrum; significant advancement is thus necessary now to model the infrared emission of PAHs, their presumed carriers, with enough detail to exploit the information content of the AIBs. This requires including anharmonicity in such models, and to do so systematically for all species included, requiring a difficult compromise between accuracy and efficiency. We performed a benchmark study to compare the performances of two methods in calculating anharmonic spectra, comparing them to available experimental data. One is a full quantum method, AnharmoniCaOs, relying on an ab initio potential, and the other relies on Molecular Dynamics simulations using a Density Functional based Tight Binding potential. The first one is found to be very accurate and detailed, but it becomes computationally very expensive for increasing temperature; the second is faster and can be used for arbitrarily high temperatures, but is less accurate. Still, its results can be used to model the evolution with temperature of isolated bands. We propose a new recipe to model anharmonic AIB emission using minimal assumptions on the general behaviour of band positions and widths with temperature, which can be defined by a small number of empirical parameters. Modelling accuracy will depend critically on these empirical parameters, allowing for an incremental improvement in model results, as better estimates become gradually available.
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