Pierre-Francois Loos
CNRS senior research at the Laboratoire de Chimie et Physique Quantiques in Toulouse (France) interested in electronic structure theory & excited states
- Reposted by Pierre-Francois Loos[Not loaded yet]
- Parquet theory for molecular systems: Formalism and static kernel parquet approximation pubs.aip.org/aip/jcp/arti... #compchem
Parquet theory for molecular systems: Formalism and static kernel parquet approximation
The GW approximation has become a method of choice for predicting quasiparticle properties in solids and large molecular systems, owing to its favorable accuracpubs.aip.org - Complex Absorbing Potential Green’s Function Methods for Resonances | Journal of Chemical Theory and Computation pubs.acs.org/doi/10.1021/... #compchem
Complex Absorbing Potential Green’s Function Methods for Resonances
The complex absorbing potential (CAP) formalism has been successfully employed in various wave function-based methods to study electronic resonance states. In contrast, Green’s function-based methods ...pubs.acs.org Analytic $G_0W_0$ gradients based on a double-similarity transformation equation-of-motion coupled-cluster treatment
The accurate prediction of ionization potentials (IPs) is central to understanding molecular reactivity, redox behavior, and spectroscopic properties. While vertical IPs can be accessed directly from ...arxiv.org- Fully Analytic Nuclear Gradients for the Bethe–Salpeter Equation | The Journal of Physical Chemistry Letters pubs.acs.org/doi/10.1021/... #compchem
Fully Analytic Nuclear Gradients for the Bethe–Salpeter Equation
The Bethe–Salpeter equation (BSE) formalism, combined with the GW approximation for ionization energies and electron affinities, is emerging as an efficient and accurate method for predicting optical excitations in molecules. In this Letter, we present the first derivation and implementation of fully analytic nuclear gradients for the BSE@G0W0 method. Building on recent developments for G0W0 nuclear gradients, we derive analytic nuclear gradients for several BSE@G0W0 variants. We validate our implementation against numerical gradients and compare excited-state geometries and adiabatic excitation energies obtained from different BSE@G0W0 variants with those from state-of-the-art wave function methods.pubs.acs.org - Reposted by Pierre-Francois Loos[Not loaded yet]
Connections between Richardson-Gaudin States, Perfect-Pairing, and Pair Coupled-Cluster Theory
Slater determinants underpin most electronic structure methods, but orbital-based approaches often struggle to describe strong correlation efficiently. Geminal-based theories, by contrast, naturally c...arxiv.orgParquet theory for molecular systems. I. Formalism and static kernel parquet approximation
The $GW$ approximation has become a method of choice for predicting quasiparticle properties in solids and large molecular systems, owing to its favorable accuracy-cost balance. However, its accuracy ...arxiv.org- QUEST Database of Highly-Accurate Excitation Energies | Journal of Chemical Theory and Computation pubs.acs.org/doi/10.1021/... #compchem
QUEST Database of Highly-Accurate Excitation Energies
We report theoretical best estimates of vertical transition energies (VTEs) for a large number of excited states and molecules: the quest database. This database includes 1489 aug-cc-pVTZ VTEs (731 singlets, 233 doublets, 461 triplets, and 64 quartets) for both valence and Rydberg transitions occurring in molecules containing from 1 to 16 non-hydrogen atoms. Quest also includes a significant list of VTEs for states characterized by a partial or genuine double-excitation character, known to be particularly challenging for many computational methods. The vast majority of the reported values are deemed chemically accurate, that is, are within ±0.05 eV of the FCI/aug-cc-pVTZ estimate. This allows for a balanced assessment of the performance of popular excited-state methodologies. We report the results of such benchmarks for various single- and multireference wave function approaches, and provide extensive Supporting Information allowing testing of other models. All corresponding data associated with the quest database, along with analysis tools, can be found in the associated GitHub repository at the following URL: https://github.com/pfloos/QUESTDB.pubs.acs.org Complex Absorbing Potential Green's Function Methods for Resonances
The complex absorbing potential (CAP) formalism has been successfully employed in various wavefunction-based methods to study electronic resonance states. In contrast, Green's function-based methods a...arxiv.orgFully Analytic Nuclear Gradients for the Bethe--Salpeter Equation
The Bethe-Salpeter equation (BSE) formalism, combined with the $GW$ approximation for ionization energies and electron affinities, is emerging as an efficient and accurate method for predicting optica...arxiv.org- 🦣 update of #QUESTDB (Database of Highly-Accurate Excitation Energies) 🦖 The latest #preprint on #QUESTDB is just out on @arXiv (arxiv.org/abs/2506.11590) with the corresponding @github repo (github.com/pfloos/QUESTDB) where we have compiled all the data in various formats. Please share! #compchem
The QUEST Database of Highly-Accurate Excitation Energies
We report theoretical best estimates of vertical transition energies (VTEs) for a large number of excited states and molecules: the \textsc{quest} database. This database includes 1489 \emph{aug}-cc-p...arxiv.org - Reposted by Pierre-Francois Loos[Not loaded yet]
- Reposted by Pierre-Francois Loos[Not loaded yet]
- Excited states of the uniform electron gas pubs.aip.org/aip/jcp/arti...
Excited states of the uniform electron gas
The uniform electron gas (UEG) is a cornerstone of density-functional theory (DFT) and the foundation of the local-density approximation, one of the most succespubs.aip.org Comparing Perturbative and Commutator-Rank-Based Truncation Schemes in Unitary Coupled-Cluster Theory
Unitary coupled cluster (UCC) theory offers a promising Hermitian alternative to conventional coupled cluster (CC) theory, but its practical implementation is hindered by the non-truncating nature of ...arxiv.orgDriven similarity renormalization group with a large active space: Applications to oligoacenes, zeaxanthin, and chromium dimer
We present a new implementation of the driven similarity renormalization group (DSRG) based on a density matrix renormalization group (DMRG) reference. The explicit build of high-order reduced density...arxiv.orgUsing Matrix-Free Tensor-Network Optimizations to Construct a Reduced-Scaling and Robust Second-Order Møller-Plesset Theory
We investigate the application of the canonical polyadic decomposition (CPD) to the tensor hypercontraction (THC) and Laplace transform (LT) approximated second-order Møller-Plesset (MP2) method. By i...arxiv.orgA Guide to Molecular Properties from the Bethe-Salpeter Equation
The Bethe-Salpeter equation (BSE) combined with the Green's function GW method has successfully transformed into a robust computational tool to describe light-matter interactions and excitation spectr...arxiv.orgThe Conundrum of Diffuse Basis Sets: A Blessing for Accuracy yet a Curse for Sparsity
Diffuse atomic orbital basis sets have proven to be essential to obtain accurate interaction energies, especially in regard to non-covalent interactions. However, they also have a detrimental impact o...arxiv.orgSimple and efficient computational strategies for calculating orbital energies and pair-orbital energies from pCCD-based methods
We introduce affordable computational strategies for calculating orbital and pair-orbital energies in atomic and molecular systems. Our methods are based on the pair Coupled Cluster Doubles (pCCD) ans...arxiv.orgExcited States of the Uniform Electron Gas
The uniform electron gas (UEG) is a cornerstone of density-functional theory (DFT) and the foundation of the local-density approximation (LDA), one of the most successful approximations in DFT. In thi...arxiv.org- Reposted by Pierre-Francois Loos[Not loaded yet]
- Reposted by Pierre-Francois LoosOh my! Thank you! 😊
- Hi Australian Researchers. I have a plan. Let's thank the amazing @arc-tracker.bsky.social for a decade of selfless work by nominating them for a Eureka Prize (Leadership in science). Are you with me? If so, repost this. Please also reply and state your support for this quest. We can do this people.
Exploring the accuracy of the equation-of-motion coupled-cluster band gap of solids
While the periodic equation-of-motion coupled-cluster (EOM-CC) method promises systematic improvement of electronic band gap calculations in solids, its practical application at the singles and double...arxiv.orgImpact of Parametrizations of the One-Body Reduced Density Matrix on the Energy Landscape
Many electronic structure methods rely on the minimization of the energy of the system with respect to the one-body reduced density matrix (1RDM). To formulate a minimization algorithm, the 1RDM is of...arxiv.orgTensor network state methods and quantum information theory for strongly correlated molecular systems
A brief pedagogical overview of recent advances in tensor network state methods are presented that have the potential to broaden their scope of application radically for strongly correlated molecular ...arxiv.orgOptimal-Reference Excited State Methods: Static Correlation at Polynomial Cost with Single-Reference Coupled-Cluster Approaches
Accurate yet efficient modeling of chemical systems with pronounced static correlation in their excited states remains a significant challenge in quantum chemistry, as most electronic structure method...arxiv.orgFreeze-and-release direct optimization method for variational calculations of excited electronic states
Time-independent, orbital-optimized density functional approaches outperform time-dependent density functional theory (TDDFT) in calculations of excited electronic states involving a large rearrangeme...arxiv.orgEquation-of-motion internally contracted multireference unitary coupled-cluster theory
The accurate computation of excited states remains a challenge in electronic structure theory, especially for systems with a ground state that requires a multireference treatment. In this work, we int...arxiv.orgExcited State Absorption: Reference Oscillator Strengths, Wavefunction and TD-DFT Benchmarks
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 modeli...arxiv.orgSelf-Refinement of Auxiliary-Field Quantum Monte Carlo via Non-Orthogonal Configuration Interaction
For optimal accuracy, auxiliary-field quantum Monte Carlo (AFQMC) requires trial states consisting of multiple Slater determinants. We develop an efficient algorithm to select the determinants from an AFQMC random walk eliminating the need for other methods. When determinants contribute significantly to the non-orthogonal configuration interaction energy, we include them in the trial state. These refined trial wave functions significantly reduce the phaseless bias and sampling variance of the local energy estimator. With 100 to 200 determinants, we lower the error of AFQMC by up to a factor of 10 for second row elements that are not accurately described with a Hartree-Fock trial wave function. For the HEAT set, we improve the average error to within the chemical accuracy. For benzene, the largest studied system, we reduce AFQMC error by 80% with 214 Slater determinants and find a 10-fold increase of the time to solution. We show that the remaining error of the method prevails in systems with static correlation or strong spin contamination.arxiv.orgIs fixed-node diffusion quantum Monte Carlo reproducible?
Fixed-node diffusion quantum Monte Carlo (FN-DMC) is a widely-trusted many-body method for solving the Schrödinger equation, known for its reliable predictions of material and molecular properties. Fu...arxiv.orgImproving Aufbau Suppressed Coupled Cluster Through Perturbative Analysis
Guided by perturbative analysis, we improve the accuracy of Aufbau suppressed coupled cluster theory in simple single excitations, multi-configurational single excitations, and charge transfer excitat...arxiv.orgDirect unconstrained optimization of excited states in density functional theory
Orbital-optimized density functional theory (DFT) has emerged as an alternative to time-dependent (TD) DFT capable of describing difficult excited states with significant electron density redistributi...arxiv.orgAutomated Quantum Chemistry Code Generation with the p$^\dagger$q Package
This article summarizes recent updates to the p$^\dagger$q package, which is a C++ accelerated Python library for generating equations and computer code corresponding to singly-reference many-body qua...arxiv.orgRichardson-Gaudin states of non-zero seniority I: matrix elements
Seniority-zero wavefunctions describe bond-breaking processes qualitatively. As eigenvectors of a model Hamiltonian, Richardson-Gaudin states provide a clear physical picture and allow for systematic ...arxiv.orgStrong coupling Møller-Plesset perturbation theory
Perturbative approaches are methods to efficiently tackle many-body problems, offering both intuitive insights and analysis of correlation effects. However, their application to systems where light an...arxiv.org- Reposted by Pierre-Francois Loos[Not loaded yet]
