Lucien Dupuy, Toni Chiti, Jeremy Morere and Emmanuel Fromager published a new paper, “Ensemble density functional theory of excited states: Exact N-centered formalism and practical opportunities” in The Journal of Chemical Physics: https://doi.org/10.1063/5.0338167

Ground-state electronic structure calculations using Kohn–Sham density functional theory (KS-DFT) offer an unprecedented balance between efficiency and accuracy, now paradigmatic to the fields of quantum chemistry and condensed matter physics. KS-DFT can be extended to model electronic excitations through density mapping onto a non-interacting ensemble state in which, unlike in thermal theories, the weights assigned to the excited states vary independently. Ensemble DFT (eDFT) has lately become a vibrant area of research thanks to its numerous appeals, such as the adequate treatment of multiple excitations for which the widely used time-dependent extension of DFT struggles. Recently, an enlarged type of ensemble, referred to as a N-centered (Nc) ensemble, has been introduced to describe within the same unified formalism both neutral and charged electronic excitations. This perspective paper provides a detailed exposition of exact Nc-eDFT, with a comprehensive review of its formal developments. To cut practical computational tools out of the exact theory, three original strategies are presented, complementing existing approaches. The first one, related to the design of ensemble density-functional approximations, consists in recycling regular ground-state functionals by dressing them with a weight-dependent scaling function deduced from exact properties of eDFT. We then explore quasi-degenerate formulations of ensemble density-functional perturbation theory, suggesting alternative definitions for the ensemble Hartree, exchange, and correlation energies, individually, and paving the way toward robust orbital-dependent eDFAs. Finally, we revisit and generalize the concept of quantum bath for an ensemble of non-interacting states, laying the foundations of an in-principle exact (in the sense of lattice eDFT) quantum embedding theory of excited states.

L’article A new publication by Lucien Dupuy, Toni Chiti, Jeremy Morere and Emmanuel Fromager est apparu en premier sur Laboratoire de Chimie Quantique de Strasbourg.

Lucien Dupuy, Emmanuel Fromager and coworker published a new paper, “Exactly Factorized Molecular Kohn–Sham Density Functional Theory” in the Journal of Computational Chemistry: https://doi.org/10.1002/jcc.70459

Fromager and Lasorne [Electron. Struct. 6 025002 (2024)] have recently derived an in-principle exact Kohn–Sham density functional theory (KS-DFT) of electrons and nuclei, where the nuclear density and the (so-called conditional) electronic density are mapped onto a fictitious electronically non-interacting KS molecule. In this work, we apply the exact factorization formalism to the molecular KS wavefunction, thus leading to disentangled (but coupled) marginal and conditional KS equations. We show that, while being equivalent to the original theory, these equations open new perspectives in the practical extension of regular (electronic) KS-DFT beyond the Born Oppenheimer approximation. The importance and treatment of correlations induced in this context by second-order geometrical derivatives is also discussed.

L’article A new publication by Lucien Dupuy, Emmanuel Fromager and coworker est apparu en premier sur Laboratoire de Chimie Quantique de Strasbourg.

Wafa Makhlouf, Emmanuel Fromager and coworker published a new paper, “Generalized local potential functional embedding theory of localized orbitals” in Electronic Structure : https://doi.org/10.1088/2516-1075/ae8066

In this work we introduce a generalized flavor, in the sense of generalized Kohn-Sham density functional theory (gKS-DFT), of the recently derived local potential functional embedding theory (LPFET) (J. Chem. Theory Comput. 2025 21 10293), where the in-principle exact formalism of DFT is combined with that of density matrix embedding theory (DMET). In generalized LPFET (gLPFET), the embedding clusters are designed from a full-size gKS system where the (in-principle non-local) Hartree-Fock exchange potential is combined with a local (in the localized orbital representation) correlation potential. The latter is optimized self-consistently such that gKS and local embedding cluster’s densities match. Unlike in DMET, which uses the same (global) chemical potential value in all clusters, each embedded orbital has its own chemical potential in gLPFET. We show analytically that, when electron correlation is strongly local, the latter potential becomes a simple functional of the correlation potential. Numerical calculations on model systems confirm the high accuracy of gLPFET in this regime, in contrast to DMET. Moreover, we show that gLPFET completely fixes the flaw of LPFET in weaker correlation regimes, through its appropriate description of the Hartree-exchange potential.

L’article A new publication by Wafa Makhlouf, Emmanuel Fromager and coworker est apparu en premier sur Laboratoire de Chimie Quantique de Strasbourg.

Loris Delafosse, Vincent Robert and Saad Yalouz published a new paper, “Orthogonally constrained CASSCF framework: Newton–Raphson orbital optimization and nuclear gradients” in The Journal of Chemical Physics : https://doi.org/10.1063/5.0324860

In a recent work [S. Yalouz and V. Robert, J. Chem. Theory Comput. 19, 1381 (2023)], we introduced the foundations of an orthogonally constrained complete active space self-consistent field (OC-CASSCF) framework that produces state-specific molecular orbitals for mutually orthogonal multiconfigurational electronic states. In the present study, we extend this approach by incorporating a Newton–Raphson orbital-optimization scheme, for which we derive the analytical expressions of the orbital gradient and Hessian. Furthermore, we outline a practical route toward the evaluation of analytical nuclear gradients, enabling geometry optimizations within the OC-CASSCF formalism. Benchmark calculations on the three lowest singlet states of LiH and H2O molecules demonstrate a systematic improvement as compared to conventional state-averaged CASSCF, even when using modestly sized active spaces.

L’article A new publication by Loris Delafosse, Vincent Robert and Saad Yalouz est apparu en premier sur Laboratoire de Chimie Quantique de Strasbourg.

A new preprint by Lucien Dupuy, Toni Chiti, Jérémy Morere and Emmanuel Fromager on Ensemble density functional theory of excited states: Exact N-centered formalism and practical opportunities is now available on arXiv : https://arxiv.org/abs/2604.11191

L’article A new preprint by Lucien Dupuy, Toni Chiti, Jérémy Morere and Emmanuel Fromager est apparu en premier sur Laboratoire de Chimie Quantique de Strasbourg.

A new preprint by Saad Yalouz and coworker on Light-Induced Quantum Self-Trapping of Vibrational Excitons in an Optical Cavity is now available on arXiv: https://arxiv.org/abs/2604.06142

L’article A new preprint by Saad Yalouz and coworker est apparu en premier sur Laboratoire de Chimie Quantique de Strasbourg.

A new preprint by Vincent Robert, Giovanni Li Manni and coworkers on Stochastic Difference-Dedicated Configuration Interaction for Magnetic Exchange in Large Active Spaces is now available on ChemRxiv : https://chemrxiv.org/doi/full/10.26434/chemrxiv.15001030/v1

L’article A new preprint by Vincent Robert, Giovanni Li Manni and coworkers est apparu en premier sur Laboratoire de Chimie Quantique de Strasbourg.

Roberto Marquardt and coworkers published a new paper, “Observation and modeling of bound–bound and bound-free transitions in Cu₂” in The Journal of Chemical Physics : https://doi.org/10.1063/5.0312177

Laser-induced transitions from the perturbed J0⁺_u , v′= 0 − 2 ∼ G 0⁺_u , v′= 62 − 68 system to the X¹Σ⁺_g (0⁺_g ) ground state of dicopper havebeen investigated experimentally and theoretically. Upon excitation of specific rotational levels, long progressions to vibrational levels are observed. Strong emissions are observed at low vibrational levels. Notably, spectra show significant line strength near and above the asymptotic atom dissociation limit. The latter feature is due to the Condon internal diffraction of bound-free transitions to the continuum region of the ground state. Based on the Rydberg–Klein–Rees potentials for the J0⁺_u , G0⁺_u , and X¹Σ⁺_g (0⁺_g ) states, eigenvalues and wave functions are obtained by solving the radial Schrödinger equation. Hence, frequencies of rovibrational transitions, Franck–Condon factors, and Einstein coefficients for spontaneous emissions are determined. The required transition dipole moment functions are obtained from high-level electronic structure calculations at the multi-reference configuration-interaction level of theory. Simulated line positions and relative intensities for transitions near and above the dissociation limit are in good agreement with the experiment. Furthermore, the feasibility of photoassociation experiments involving ultracold copper atoms is estimated by calculating the coupling rate between the colliding cold atoms and the excited G0⁺_u state.

L’article A new publication by Roberto Marquardt and coworkers est apparu en premier sur Laboratoire de Chimie Quantique de Strasbourg.

A new preprint by Wafa Makhlouf, Emmanuel Fromager and coworker on Generalized local potential functional embedding theory of localized orbitals is now available on arXiv: https://arxiv.org/abs/2602.15624

L’article A new preprint by Wafa Makhlouf, Emmanuel Fromager and coworker est apparu en premier sur Laboratoire de Chimie Quantique de Strasbourg.

A new preprint by Lucien Dupuy and Emmanuel Fromager on Charged excitations made neutral: N-centered ensemble density functional theory of Fukui functions is now available on arXiv: https://arxiv.org/abs/2601.02985

L’article A new preprint by Lucien Dupuy and Emmanuel Fromager est apparu en premier sur Laboratoire de Chimie Quantique de Strasbourg.