Premium
Improving the predictive quality of time‐dependent density functional theory calculations of the X‐ray emission spectroscopy of organic molecules
Author(s) -
Fouda Adam A. E.,
Besley Nicholas A.
Publication year - 2020
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.26153
Subject(s) - time dependent density functional theory , density functional theory , spectral line , hybrid functional , relaxation (psychology) , chemistry , emission spectrum , atomic orbital , atomic physics , spectroscopy , range (aeronautics) , molecular physics , computational chemistry , materials science , physics , electron , quantum mechanics , psychology , social psychology , composite material
The simulation of X‐ray emission spectra of organic molecules using time‐dependent density functional theory (TDDFT) is explored. TDDFT calculations using standard hybrid exchange‐correlation functionals in conjunction with large basis sets can predict accurate X‐ray emission spectra provided an energy shift is applied to align the spectra with experiment. The relaxation of the orbitals in the intermediate state is an important factor, and neglect of this relaxation leads to considerably poorer predicted spectra. A short‐range corrected functional is found to give emission energies that required a relatively small energy shift to align with experiment. However, increasing the amount of Hartree–Fock exchange in this functional to remove the need for any energy shift led to a deterioration in the quality of the calculated spectral profile. To predict accurate spectra without reference to experimental measurements, we use the CAM‐B3LYP functional with the energy scale determined with reference to a Δself‐consistent field calculation for the highest energy emission transition.