TD-CI Simulation of the Electronic Optical Response of Molecules in Intense Fields II: Comparison of DFT Functionals and EOM-CCSD

Abstract

Time-dependent configuration interaction (TD-CI) simulations can be used to simulate molecules in intense laser fields. TD-CI calculations use the excitation energies and transition dipoles calculated in the absence of a field. The EOM-CCSD method provides a good estimate of the field-free excited states but is rather expensive. Linear-response time-dependent density functional theory (TD-DFT) is an inexpensive alternative for computing the field-free excitation energies and transition dipoles needed for TD-CI simulations. Linear-response TD-DFT calculations were carried out with standard functionals (B3LYP, BH&HLYP, HSE2PBE (HSE03), BLYP, PBE, PW91, and TPSS) and long-range corrected functionals (LC-ωPBE, ωB97XD, CAM-B3LYP, LC-BLYP, LC-PBE, LC-PW91, and LC-TPSS). These calculations used the 6-31G(d,p) basis set augmented with three sets of diffuse sp functions on each heavy atom. Butadiene was employed as a test case, and 500 excited states were calculated with each functional. Standard functionals yield average excitation energies that are significantly lower than the EOM-CC, while long-range corrected functionals tend to produce average excitation energies slightly higher. Long-range corrected functionals also yield transition dipoles that are somewhat larger than EOM-CC on average. The TD-CI simulations were carried out with a three-cycle Gaussian pulse (ω = 0.06 au, 760 nm) with intensities up to 1.26 × 10(14) W cm(-2) directed along the vector connecting the end carbons. The nonlinear response as indicated by the residual populations of the excited states after the pulse is far too large with standard functionals, primarily because the excitation energies are too low. The LC-ωPBE, LC-PBE, LC-PW91, and LC-TPSS long-range corrected functionals produce responses comparable to EOM-CC.

Cytosine Radical Cations: A Gas‐Phase Study Combining IRMPD Spectroscopy, UVPD Spectroscopy, Ion–Molecule Reactions, and Theoretical Calculations

“…Vertical excitation energies and transition intensities (oscillator strengths) were calculated for the 25 lowest energy excited states with time-dependent DFT (TD-DFT) calculations [41] using the wB97X-D and M06-2X functionals and the 6-311 + G(2d,p) basis set. [43] The EOM-CCSD/6-31 + G(d,p) and 6-311 + G(2d,p) calculations on 4 and 8 showed nearly identical results (Table S2) with root mean square deviations of absorption wavelengths of < 2.3 nm. [43] The EOM-CCSD/6-31 + G(d,p) and 6-311 + G(2d,p) calculations on 4 and 8 showed nearly identical results (Table S2) with root mean square deviations of absorption wavelengths of < 2.3 nm.…”

“…Another set of excitation energies was obtained with equation-of-motion calculations with coupled clusters and single and double excitations (EOM-CCSD) [42] using the 6-31 + G(d,p) basis set and, for structures 4 and 8 also using the 6-311 + G(2d,p) basis set, to benchmark the TD-DFT energies. [43] The EOM-CCSD/6-31 + G(d,p) and 6-311 + G(2d,p) calculations on 4 and 8 showed nearly identical results (Table S2) with root mean square deviations of absorption wavelengths of < 2.3 nm. The smaller 6-31 + G(d,p) basis set was then used in EOM-CCSD calculations of all cytosine cation radicals.…”

Equation of motion for the solvent polarization apparent charges in the polarizable continuum model: Application to time-dependent CI

“…Furthermore for the same simulation we have checked the quality of the approximation made in eq. (27): at the end of the simulation the contribution of the HF state to the ground state is higher than 99.99%.…”

Molecular Dynamics of Methylamine, Methanol, and Methyl Fluoride Cations in Intense 7 Micron Laser Fields

“…The amount of Hartree−Fock exchange in CAM-B3LYP increases from 19% at short-range to 65% at long-range (0.33 range parameter) and should be better than B3LYP at describing the long-range exchange behavior of the density distorted by the strong laser field. 16 The interaction of the molecule with the laser field was calculated in the semiclassical dipole approximation. (1) μ⃗ is the dipole operator, E ⃗ (t) is the electric field component of the laser, and s⃗ (t) describes the shape of the pulse.…”