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.

A new preprint by Lucien Dupuy, Emmanuel Fromager and coworker on Exactly factorized molecular Kohn–Sham density functional theory is now available on the arXiv: https://arxiv.org/abs/2601.03972

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

Vincent Robert and coworkers published a new paper, “Dynamic Electromerism: Correlated Rotational and Cross-Conjugation Dynamics in DAMN (DiAminoMaleoNitrile) and DAFN (DiAminoFumaroNitrile) Derivatives” in the Journal of the American Chemical Society : https://doi-org.scd-rproxy.u-strasbg.fr/10.1021/jacs.5c09269

Conformational dynamics play key roles in molecular reactivity and the development of functional molecular machines. In this study, we investigate the competitive correlation between internal rotations about the C–NR₂ bonds and cross-conjugation dynamics in DAMN, DAFN, and their derivatives. Using a combination of NMR spectroscopy, crystallographic analysis, and computational studies, we demonstrate that conjugation in one of the two push–pull π-systems restricts its own C–N bond rotation while suspending conjugation and facilitating rotation in the other system, leading to synchronized rotation-conjugation oscillation. Variable Temperature (VT)-NMR spectroscopy revealed that the presence of competing cross-conjugated pathways drastically lowers the C–N rotational barriers of the amino groups compared to those of reference compounds presenting a single π-system (11–14 kcal/mol at 298 K). Density functional theory (DFT) studies yielded rotational barriers as low as ∼2 kcal/mol for tetra-methylated DAMN, with a disrotatory mechanism. The introduction of steric effects increased the rotational barriers, yielding measurable NMR values of 7–9 kcal/mol at coalescence in the bulkiest DAMN derivative. Additionally, modulation of the structural desymmetrization of the coupled push–pull systems in monoimine derivatives of DAMN allowed determination of rotational barriers within the range of those of the reference compounds. These effects agreed with the presence of cross-conjugation, which was also supported by X-ray diffraction. The findings provide insight into the structural factors governing rotational barriers in cross-conjugated systems exhibiting correlated molecular motion. Thus, DAMN and DAFN present a dynamic electromerism process where oscillation between two different cross-conjugation pathways is regulated by the C–N rotation frequency.

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

Even Chiari, Wafa Makhlouf, Lucie Pepe, Saad Yalouz and coworkers published a new paper, “Ab initio polaritonic chemistry on diverse quantum computing platforms: Ansatz circuit design for qubit, qudit, and hybrid qubit-qumode architectures” in Physical Review A : https://doi.org/10.1103/1l5j-dfh4

In the field of ab initio polaritonic chemistry, the use of quantum computers may offer, in the long term, a promising computational pathway for simulating and exploring novel cavity-induced light-matter phenomena. Addressing such problems on emerging platforms, however, already presents significant challenges that need to be considered for near-term applications. Within the framework of the variational quantum eigensolver (VQE), a key question concerns the development of quantum circuit Ansätze capable of encoding strongly correlated electron-photon states at a reasonable resource cost. Motivated by this question, in this work we develop different Ansatz strategies covering not only conventional qubit-based approaches but also higher-dimensional information units. Specifically, we introduce a set of circuits tailored to three different quantum computing architectures: (i) qubits, (ii) qudits, and (iii) hybrid qubit-qumode units of information. All circuits are designed to be both compact and physically motivated, with a central element being the development of spin-adapted electron-photon entangling fragment circuits tailored to the native capabilities of each platform. Integrating the different Ansätze within the state-averaged VQE, we numerically benchmark the three strategies on a cavity-embedded H₂ molecule using state-vector simulations. Our results show that each proposed Ansatz achieves high accuracy in encoding the ground, first, and second polaritonic eigenstates of the system, even reproducing characteristic light-matter phenomena such as light-induced avoided crossings and conical intersections. This prospective work, beyond introducing multiple computational strategies adapted to different platforms, also highlights the potential of higher-dimensional quantum architectures to address hybrid fermion-boson systems.

L’article A new publication by Even Chiari, Wafa Makhlouf, Lucie Pepe, Saad Yalouz and coworkers est apparu en premier sur Laboratoire de Chimie Quantique de Strasbourg.