Rani Vadala Jhansi, Kanakati Arun Kumar, Mahapatra S
School of Chemistry, University of Hyderabad, Hyderabad 500046, India.
J Chem Phys. 2024 Sep 7;161(9). doi: 10.1063/5.0215910.
In this article, the theoretical photoionization spectroscopy of the aziridine (C2H5N) molecule is investigated. To start with, we have optimized the geometry of this molecule at the neutral electronic ground state at the density functional theory/augmented correlation-consistent polarized valence triple zeta level of theory using the G09 program. The electronic structure calculations were restricted to the first six low-lying electronic states in order to account for the experimental photoelectron spectrum of the C2H5N molecule. The first six low-lying electronic states (X̃2A', Ã2A', B̃2A″, C̃2A″, D̃2A', and Ẽ2A') of the potential energy surfaces (PESs) are calculated by both equation of motion-ionization potential-coupled cluster singles and doubles and multi-configuration quasi-degenerate perturbation theory ab initio quantum chemistry methods along the dimensionless normal displacement coordinates in which multiple conical intersections were established among the considered electronic states. A (6 × 6) model vibronic Hamiltonian is constructed on a diabatic electronic basis, using the symmetry selection rules and Taylor series expansion. The Cs symmetry point group of the aziridine molecule leads to electronic states symmetry of either A' or A″, and these states are close in energy, due to which the same symmetry electronic states avoid each other. To get a smooth diabatic PES, a fourfold diabatization scheme is used, which is implemented in the General Atomic and Molecular Electronic Structure Systems suite of programs. All the parameters used in the diabatic vibronic coupling model Hamiltonian are calculated in terms of the normal modes of vibrational coordinates. Finally, the vibronic model Hamiltonian constructed for the coupled six electronic states is used to solve both time-independent and time-dependent Schrödinger equations using the multi-configuration time-dependent Hartree program module to obtain the dynamical observables. The theoretical vibronic band structure is found to be in good accord with the available experimental results.
在本文中，对氮丙啶（C₂H₅N）分子的理论光电离光谱进行了研究。首先，我们使用G09程序在密度泛函理论/增强相关一致极化价三重ζ理论水平下，对该分子在中性电子基态的几何结构进行了优化。电子结构计算限于前六个低能电子态，以便与C₂H₅N分子的实验光电子能谱相符。通过运动方程 - 电离势 - 耦合簇单双激发方法和多组态准简并微扰理论从头算量子化学方法，沿着无量纲的法向位移坐标计算了势能面（PES）的前六个低能电子态（X̃²A'、òA'、B̃²A″、C̃²A″、D̃²A'和Ẽ²A'），在所考虑的电子态之间建立了多个锥形交叉点。利用对称选择规则和泰勒级数展开，在非绝热电子基上构建了一个(6×6)模型振动电子哈密顿量。氮丙啶分子的Cs对称点群导致电子态对称类型为A'或A″，并且这些态能量相近，因此相同对称类型的电子态相互回避。为了得到一个平滑的非绝热PES，使用了一种四重非绝热方案，该方案在通用原子和分子电子结构系统程序套件中实现。非绝热振动耦合模型哈密顿量中使用的所有参数均根据振动坐标的正则模式进行计算。最后，利用多组态含时哈特里程序模块，将为耦合的六个电子态构建的振动电子模型哈密顿量用于求解含时和不含时薛定谔方程，以获得动力学可观测量。理论振动电子能带结构与现有的实验结果吻合良好。
