Premium
A theoretical study of the photoelectron spectra of dichloroketene with accurate computation of ionization energies via complete basis set limit extrapolation
Author(s) -
Chang JiaLin,
Hsieh JungHang,
Huang YunJhu,
Chen ChiingChang,
Chang MuFong
Publication year - 2019
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.25866
Subject(s) - extrapolation , basis set , ionization energy , chemistry , ionization , excited state , ground state , atomic physics , spectral line , ansatz , physics , computational chemistry , ion , quantum mechanics , density functional theory , mathematics , mathematical analysis , organic chemistry
Abstract We calculated the equilibrium geometries and harmonic vibrational frequencies of the ground state and five cationic states of dichloroketene using (TD‐)B3LYP, PBE0, and M06/M06‐2X approaches. The photoelectron spectra of dichloroketene were simulated by computing Franck‐Condon factors. The ionization energies were computed using the CCSD(T) approach with extrapolation to the complete basis set (CBS) limit. We propose two new CBS energy formulas ( E = E CBS + A exp(‐ x ) + B /( x −1) n , n = 2 or 3) and compare the performance of different CBS approaches. A new ionic state of dichloroketene belonging to the C s point group is reported. This state is identified as the first excited state of Cl 2 CCO + having a double‐well potential‐energy curve along the CCO bending mode with a barrier height of 1.335 eV. The simulated photoelectron spectra are in agreement with the experiment. The vertical ionization energies calculated via spectral simulation are more accurate compared with those obtained at the ground‐state structure. Among the CBS formulas used, the proposed ansatz with n = 2 performs best, with a mean absolute error of 0.021 and 0.012 eV for the adiabatic and vertical ionization energies, respectively.