Intermolecular configurations dominated by quadrupole-quadrupole electrostatic interactions: explicit correlation treatment of the five-dimensional potential energy surface and infrared spectra for the CO-N-2 complex
Intermolecular configurations dominated by quadrupole-quadrupole electrostatic interactions: explicit correlation treatment of the five-dimensional potential energy surface and infrared spectra for the CO-N-2 complex
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四极-四极静电相互作用主导的分子间构型：CO-N-2配合物五维势能面和红外光谱的显式关联处理
DOI：
10.1039/c7cp06854a
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Hui Li
中科院分区：
文献类型：
--
作者：
Jingmin Liu;Yu Zhai;Xiaolong Zhang;Hui Li
由于范德华配合物的弱相互作用、软塌性和非谐性，对其分子间构型的深入理解是一个巨大的挑战。尽管高分辨率微波或红外光谱提供了最直接和精确的实验证据之一，但在确定范德华体系的这种分子间构型方面，起源和关键作用在很大程度上取决于其高度精确的势能面（PES）和对其反振动波函数的详细分析。本文采用显式相关偶对簇（CCSD(T)-F12）方法，结合一个大基集，生成了CO - n2范德华配合物的一个新的五维势能面，该势能面明确地包含了对CO单体拉伸坐标的依赖。将v = 0和v = 1时的振动平均相互作用能与莫尔斯/远程势模（VMLR）进行最小二乘拟合，得到解析四维ps。对于v = 0和v = 1，这些拟合到7966个点的均方根偏差（RMSD）分别为0.131 cm - 1和0.129 cm - 1，只有315个参数。进行了能量分解分析，发现控制分子间构型的主要因素是四极-四极静电相互作用。此外，还首次得到了结构的旋转振动水平和波函数。预测的邻位n2 - co配合物的红外跃迁和强度以及计算的对n2 - co的能级与现有实验数据吻合良好，RMSD差小于0.068 cm−1。邻位n_2 - CO的计算红外波段原点位移与CO基频相关为−0.721 cm−1，与实验值−0.739 cm−1非常吻合。与实验值的一致性验证了PESs的高质量，并增强了我们解释观测到的2163 cm−1附近的神秘线的信心。
A thorough understanding of the intermolecular configurations of van der Waals complexes is a great challenge due to their weak interactions, floppiness and anharmonic nature. Although high-resolution microwave or infrared spectroscopy provides one of the most direct and precise pieces of experimental evidence, the origin and key role in determining such intermolecular configurations of a van der Waals system strongly depend on its highly accurate potential energy surface (PES) and a detailed analysis of its ro-vibrational wavefunctions. Here, a new five-dimensional potential energy surface for the van der Waals complex of CO–N2 which explicitly incorporates the dependence on the stretch coordinate of the CO monomer is generated using the explicitly correlated couple cluster (CCSD(T)-F12) method in conjunction with a large basis set. Analytic four-dimensional PESs are obtained by the least-squares fitting of vibrationally averaged interaction energies for v = 0 and v = 1 to the Morse/Long-Range potential mode (VMLR). These fits to 7966 points have root-mean-square deviations (RMSD) of 0.131 cm−1 and 0.129 cm−1 for v = 0 and v = 1, respectively, with only 315 parameters. Energy decomposition analysis is carried out, and it reveals that the dominant factor in controlling intermolecular configurations is quadrupole–quadrupole electrostatic interactions. Moreover, the rovibrational levels and wave functions are obtained for the first time. The predicted infrared transitions and intensities for the ortho-N2–CO complex as well as the calculated energy levels for para-N2–CO are in good agreement with the available experimental data with RMSD discrepancies smaller than 0.068 cm−1. The calculated infrared band origin shift associated with the fundamental band frequency of CO is −0.721 cm−1 for ortho-N2–CO which is in excellent agreement with the experimental value of −0.739 cm−1. The agreement with experimental values validates the high quality of the PESs and enhances our confidence to explain the observed mystery lines around 2163 cm−1.