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Excited-state absorption (ESA) corresponds to the transition between two electronic excited states and is a fundamental process for probing and understanding light-matter interactions. Accurate modeling of ESA is indeed often required to interpret time-resolved experiments. In this contribution, we present a dataset of 53 ESA oscillator strengths in three different gauges and the associated vertical transition energies between 71 excited states of 23 small- and medium-sized molecules from the QUEST database. The reference values were obtained within the quadratic-response (QR) CC3 formalism using eight different Dunning basis sets. We found that the d-aug-cc-pVTZ basis set is always adequate while its more compact double-$\zeta$ counterpart, d-aug-cc-pVDZ, performs well in most applications. These QR-CC3 data allow us to assess the performance of QR-TDDFT, with and without applying the Tamm-Dancoff approximation, using a panel of global and range-separated hybrids (B3LYP, BH{\&}HLYP, CAM-B3LYP, LC-BLYP33, and LC-BLYP47), as well as several lower-order wavefunction methods, i.e., QR-CCSD, QR-CC2, EOM-CCSD, ISR-ADC(2), and ISR-ADC(3). We show that QR-TDDFT delivers acceptable errors for ESA oscillator strengths, with CAM-B3LYP showing particular promise, especially for the largest molecules of our set. We also find that ISR-ADC(3) exhibits excellent performance
Building on our recent study [https://doi.org/10.1021/acs.jpclett.3c02052, J. Phys. Chem. Lett. 14, 8780 (2023)], we explore the generalization of the ground-state Kohn-Sham (KS) formalism of density-functional theory (DFT) to the (singlet) excited states of the asymmetric Hubbard dimer at half-filling. While we found that the KS-DFT framework can be straightforwardly generalized to the highest-lying doubly-excited state, the treatment of the first excited state presents significant challenges. Specifically, using a density-fixed adiabatic connection, we show that the density of the first excited state lacks non-interacting $v$-representability. However, by employing an analytic continuation of the adiabatic path, we demonstrate that the density of the first excited state can be generated by a complex-valued external potential in the non-interacting case. More practically, by performing state-specific KS calculations with exact and approximate correlation functionals -- each state possessing a distinct correlation functional -- we observe that spurious stationary solutions of the KS equations may arise due to the approximate nature of the functional.
Reduced density matrix functional theory (RDMFT) and coupled cluster theory restricted to paired double excitations (pCCD) are emerging as efficient methodologies for accounting for the so-called non-dynamic electronic correlation effects. Up to now, molecular calculations have been performed with real-valued orbitals. However, before extending the applicability of these methodologies to extended systems, where Bloch states are employed, the subtleties of working with complex-valued orbitals and the consequences of imposing time-reversal symmetry must be carefully addressed. In this work, we describe the theoretical and practical implications of adopting time-reversal symmetry in RDMFT and pCCD when allowing for complex-valued orbital coefficients. The theoretical considerations primarily affect the optimization algorithms, while the practical implications raise fundamental questions about the stability of solutions. Specifically, we find that complex solutions lower the energy when non-dynamic electronic correlation effects are pronounced. We present numerical examples to illustrate and discuss these instabilities and possible problems introduced by N-representability violations.
The Bethe-Salpeter equation has been extensively employed to compute the two-body electron-hole propagator and its poles which correspond to the neutral excitation energies of the system. Through a different time-ordering, the two-body Green's function can also describe the propagation of two electrons or two holes. The corresponding poles are the double ionization potentials and double electron affinities of the system. In this work, a Bethe-Salpeter equation for the two-body particle-particle propagator is derived within the linear-response formalism using a pairing field and anomalous propagators. This framework allows us to compute kernels corresponding to different self-energy approximations ($GW$, $T$-matrix, and second-Born) as in the usual electron-hole case. The performance of these various kernels is gauged for singlet and triplet valence double ionization potentials using a set of 23 small molecules. The description of double core hole states is also analyzed.
Sujets
Single-core optimization
CP violation
QSAR
Relativistic corrections
Atoms
Atomic charges
Configuration Interaction
AB-INITIO
Xenon
Ab initio calculation
Diffusion Monte Carlo
Atomic data
AB-INITIO CALCULATION
Chimie quantique
Carbon Nanotubes
A posteriori Localization
Green's function
Atrazine-cations complexes
Auto-énergie
Analytic gradient
3470+e
États excités
CIPSI
Parity violation
BENZENE MOLECULE
Quantum chemistry
Numerical calculations
Mécanique quantique relativiste
Electron correlation
Biodegradation
3115ae
Valence bond
Atomic processes
Time-dependent density-functional theory
Relativistic quantum chemistry
Azide Anion
New physics
Adiabatic connection
3115vj
3115ag
ALGORITHM
Chemical concepts
Ion
Anderson mechanism
Atomic and molecular structure and dynamics
Time reversal violation
Molecular descriptors
Petascale
Approximation GW
Dipole
Pesticide
Abiotic degradation
Dispersion coefficients
Density functional theory
3115vn
Configuration interactions
Electron electric dipole moment
Perturbation theory
Atom
Rydberg states
Théorie des perturbations
Wave functions
Atrazine
Path integral
Spin-orbit interactions
3115am
Corrélation électronique
Dirac equation
Atomic charges chemical concepts maximum probability domain population
Pesticides Metabolites Clustering Molecular modeling Environmental fate Partial least squares
Acrolein
A priori Localization
X-ray spectroscopy
Line formation
Electron electric moment
AROMATIC-MOLECULES
Fonction de Green
Hyperfine structure
Excited states
Molecular properties
Relativistic quantum mechanics
Quantum Chemistry
Parallel speedup
3115bw
Argile
Ground states
Anharmonic oscillator
Quantum Monte Carlo
Coupled cluster
Range separation
Aimantation
BIOMOLECULAR HOMOCHIRALITY
Polarizabilities
Coupled cluster calculations
Diatomic molecules
3115aj
3315Fm
Argon
Large systems
Atomic and molecular collisions