一种基于转动光谱的分子团簇结构拟合程序

A Fitting Program for Structural Determination of Molecular Clusters from Rotational Spectroscopy

分子团簇是宏观物质的构成单元,其结构的表征可以揭示单.元分子之间的相互作用、由于转动尤谱与分子团簇的质量分布直接相关,通过与高精度量子化学计算相结合,啁啾脉冲-傅里叶变换微波光谱学成为了表征分子团簇结构的有力工具.然而,由于分子团簇结构的多样性,从实验光谱中确定较大或复杂团簇的结构仍然具有很大挑战性:从头算和密度泛函搜索分子团簇的稳定结构非常耗时且高度依赖于计算方法。为了解决这些问题,本文开发了一种无需量子化学优化、仅基于实验旋转常数来搜索潜在分子团簇结构的方法.该方法通过半经验采样程序或拟蒙特卡罗万法创建初始构象集合,并采用信赖域反射算法对分子团簇进行结构拟合,从而快速生成潜在构象并获得精确的结构信息。本文在水六聚体和苯甲醛-水团簇中验证了该结构拟合程序的有效性,得到的拓扑结构与实验结果高度吻合.

The characterization of the structures of molecular clusters,which serve as building blocks for bulk substances,provides crucial insight into the interactions between constituent units.Chirpedpulse Fourier transform microwave(CP-FTMW)spectroscopy,combined with state-of-the-art quantum chemical calculations,is a powerful tool for characterizing the structures of molecular clusters,as the rotational spectra are directly related to the mass distribution of a molecule or cluster.However,determining the structures of large or complex clusters from experimental rotational spectra remains challenging due to their structural flexibility.Ab initio and density functional theory calculations for searching their stable structures could be significantly time-consuming and method-dependent.To address these challenges,we have developed an approach that relies on the experimental rotational constants to search for potential molecular structures without quantum chemical optimization.Our approach involves creating an initial set of conformers through either a semi-empirical sampling program or the quasi-Monte Carlo method.Afterward,the trust region reflective algorithm is utilized for structure fitting.This procedure enables us to quickly generate potential conformers and gain access to precise structural information.We apply our fitting program to water hexamer and benzaldehyde-water clusters,and the resulting topological structures align extremely well with the experimental results.