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arXiv 1610.03271physics.chem-ph
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甲烷分子的高精度{ \it ab initio}势能面

A highly accurate {\it ab initio} potential energy surface for methane

Alec Owens, Sergey N. Yurchenko, Andrey Yachmenev, Jonathan Tennyson, Walter Thiel

摘要:

利用最新的\textit{ab initio}理论,建立了一个新的甲烷九维势能面。PES是基于显式相关耦合集群计算外推到完整的基组限制,并采用了一系列更高级别的附加能量校正。其中包括:核心价电子相关,高阶耦合集团项超出微扰三倍,标量相对论效应和对角Born-Oppenheimer修正。子波数精度实现了大多数实验已知的振动能级与四个基本的$^{12}$ CH $_4$再现与均方根误差为$0.70{\,}$ cm $^{-1}$。计算的\textit{ab initio}平衡C{--}H键长是在良好的协议与以前的值,尽管纯旋转能量显示微小的系统误差作为$J$(旋转激发)增加。结果表明,这些误差可以显着减少,通过调整平衡的几何形状。PES代表了迄今为止最精确的\textit{ab initio}表面,并将作为经验改进的良好起点。

英文摘要:

A new nine-dimensional potential energy surface (PES) for methane has been generated using state-of-the-art \textit{ab initio} theory. The PES is based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set limit and incorporates a range of higher-level additive energy corrections. These include: core-valence electron correlation, higher-order coupled cluster terms beyond perturbative triples, scalar relativistic effects and the diagonal Born-Oppenheimer correction. Sub-wavenumber accuracy is achieved for the majority of experimentally known vibrational energy levels with the four fundamentals of $^{12}$CH$_4$ reproduced with a root-mean-square error of $0.70{\,}$cm$^{-1}$. The computed \textit{ab initio} equilibrium C{--}H bond length is in excellent agreement with previous values despite pure rotational energies displaying minor systematic errors as $J$ (rotational excitation) increases. It is shown that these errors can be significantly reduced by adjusting the equilibrium geometry. The PES represents the most accurate \textit{ab initio} surface to date and will serve as a good starting point for empirical refinement.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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