First Full-Dimensional Potential Energy and Dipole Moment Surfaces of SF6.,The Journal of Physical Chemistry A

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First Full-Dimensional Potential Energy and Dipole Moment Surfaces of SF6.
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2020-08-03 , DOI: 10.1021/acs.jpca.0c02733
Andrei V Nikitin ₁ , Michael Rey ₂ , Iana S Chizhmakova _{3,

4} , Vladimir G Tyuterev _{2,

4}

Affiliation

A 15-dimensional analytical form for the potential energy and dipole moment surfaces of the SF₆ molecule in the ground electronic state is obtained using ab initio methods. In order to calculate the equilibrium S–F distance, we applied the coupled cluster CCSD(T) method and several versions of the correlation-consistent basis sets from valence triple-zeta (VTZ) and augmented valence triple-zeta (AVTZ) to core-valence quadruple-zeta (CVQZ) with Douglas–Kroll (DK) relativistic corrections that provided good agreement with an empirical equilibrium value. Ab initio electronic energies on 15D grids of nuclear geometries are computed using the CCSD(T) method with VTZ and CVQZ-DK basis sets. The analytical representation of the potential energy surface is determined through an expansion in symmetry-adapted products of nonlinear coordinates up to the 5th order. The influence of additional redundant coordinates on the quality of the fit was investigated. Parameters of full-dimensional dipole moment surfaces are determined up to the 4th order expansion in normal mode coordinates. For validation of ab initio results, the fundamental vibration frequencies and absorption cross sections of the principal sulfur hexafluoride isotopologue are calculated, giving good agreement with cold (180 K) and room temperature (296 K) experimental spectra. Absorption cross sections calculated from our preliminary line list agree much better with these observations than the simulations using SF₆ line-by-line lists constructed from effective models included in currently available spectroscopic databases.

中文翻译：

SF6的第一个全尺寸势能和偶极矩表面。

使用从头算方法获得了基态电子状态下SF ₆分子的势能和偶极矩表面的15维分析形式。为了计算平衡SF距离，我们应用了耦合簇CCSD（T）方法以及从价三重ζ（VTZ）和增强价三重ζ（AVTZ）到核心的多个版本的相关一致基集价四元整数（CVQZ）和道格拉斯-克罗尔（DK）的相对论性修正，与经验均衡值具有良好的一致性。从头算使用带有VTZ和CVQZ-DK基集的CCSD（T）方法，计算核几何形状的15D网格上的电子能量。势能面的解析表示是通过将非线性坐标的对称适应乘积扩展到5阶来确定的。研究了附加冗余坐标对拟合质量的影响。全维偶极矩表面的参数在法向模式坐标中确定到4阶展开。用于从头算起结果，计算出了主要六氟化硫同位素异构体的基本振动频率和吸收截面，与冷（180 K）和室温（296 K）实验光谱相吻合。从我们的初步谱线列表中计算出的吸收横截面与这些观察结果相比要好得多，这比使用SF ₆谱线列表（由当前可用的光谱数据库中包含的有效模型构建）进行的模拟更好。

更新日期：2020-09-03

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