A5086592608- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Machine Learning in Materials Science
- Quantum, superfluid, helium dynamics
- Photochemistry and Electron Transfer Studies
- Advanced NMR Techniques and Applications
- Catalysis and Oxidation Reactions
- Distributed and Parallel Computing Systems
- Physics of Superconductivity and Magnetism
- Catalytic Processes in Materials Science
- Molecular Junctions and Nanostructures
- Advanced Data Storage Technologies
- History and advancements in chemistry
- Free Radicals and Antioxidants
- Parallel Computing and Optimization Techniques
- Molecular spectroscopy and chirality
- Quantum Dots Synthesis And Properties
- Electron and X-Ray Spectroscopy Techniques
- Scientific Computing and Data Management
- Theoretical and Computational Physics
- Molecular Spectroscopy and Structure
- Spectroscopy and Laser Applications
- Advanced Physical and Chemical Molecular Interactions
- X-ray Diffraction in Crystallography
- Atmospheric chemistry and aerosols
Université de Toulouse
2015-2024
Centre National de la Recherche Scientifique
2015-2024
Laboratoire de Chimie et Physique Quantiques
2015-2024
Université Toulouse III - Paul Sabatier
2013-2024
Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes
2009-2017
University of Ferrara
2016
Sorbonne Université
2002-2008
Laboratoire de Chimie Physique
2004-2008
Université Paris Cité
2004-2008
École nationale des ponts et chaussées
2006-2007
Striving to define very accurate vertical transition energies, we perform both high-level coupled cluster (CC) calculations (up CCSDTQP) and selected configuration interaction (sCI) several millions of determinants) for 18 small compounds (water, hydrogen sulfide, ammonia, chloride, dinitrogen, carbon monoxide, acetylene, ethylene, formaldehyde, methanimine, thioformaldehyde, acetaldehyde, cyclopropene, diazomethane, formamide, ketene, nitrosomethane, the smallest streptocyanine). By...
Following our previous work focussing on compounds containing up to 3 non-hydrogen atoms [\emph{J. Chem. Theory Comput.} {\bfseries 14} (2018) 4360--4379], we present here highly-accurate vertical transition energies obtained for 27 molecules encompassing 4, 5, and 6 atoms. To obtain these energies, use equation-of-motion coupled cluster theory the highest technically possible excitation order systems (CC3, EOM-CCSDT, EOM-CCSDTQ), selected configuration interaction (SCI) calculations (with...
Excited states exhibiting double excitation character are notoriously difficult to model using conventional single-reference methods, such as adiabatic time-dependent density-functional theory (TD-DFT) or equation-of-motion coupled cluster (EOM-CC). In the present work, we provide accurate reference energies for transitions involving a substantial amount of series increasingly large diffuse-containing atomic basis sets. Our set gathers 20 vertical from 14 small- and medium-size molecule....
We provide an overview of the successive steps that made possible to obtain increasingly accurate excitation energies with computational chemistry tools, eventually leading chemically vertical transition for small- and medium-size molecules. First, we describe evolution \textit{ab initio} methods employed define benchmark values, originally Roos' CASPT2 method, then CC3 method as in renowned Thiel set, more recently resurgence selected configuration interaction methods. The latter has been...
Defining accurate and compact trial wavefunctions leading to small statistical fixed-node errors in quantum Monte Carlo (QMC) calculations is still a challenging problem. Here we propose make use of selected configuration interaction (CI) expansions obtained by selecting the most important determinants through perturbative criterion. A major advantage with respect truncated CASSCF or CI limited maximum number excitations (e.g, CISD) that much smaller can be considered (many unessential are...
Quantum chemistry is a discipline which relies heavily on very expensive numerical computations. The scaling of correlated wave function methods lies, in their standard implementation, between O(N5) and O(eN) , where N proportional to the system size. Therefore, performing accurate calculations chemically meaningful systems requires (i) approximations that can lower computational (ii) efficient implementations take advantage modern massively parallel architectures. Package an open-source...
Selected configuration interaction (sCI) methods including second-order perturbative corrections provide near full CI (FCI) quality energies with only a small fraction of the determinants FCI space. Here, we introduce both state-specific and multi-state sCI method based on using selection made iteratively (CIPSI) algorithm. The present revises reference (internal) space under effect its outer via construction an effective Hamiltonian, following shifted-Bk philosophy Davidson co-workers. In...
A hybrid stochastic-deterministic approach for computing the second-order perturbative contribution E(2) within multireference perturbation theory (MRPT) is presented. The idea at heart of our scheme—based on a reformulation as sum elementary contributions associated with each determinant MR wave function—is to split into stochastic and deterministic part. During simulation, part gradually reduced by dynamically increasing until one reaches desired accuracy. In sharp contrast purely Monte...
Aiming at completing the sets of FCI-quality transition energies that we recently developed (\textit{J.~Chem.~Theory Comput.} \textbf{14} (2018) 4360--4379, \textit{ibid.}~\textbf{15} (2019) 1939--1956, and \textit{ibid.}~\textbf{16} (2020) 1711--1741), provide, in present contribution, ultra-accurate vertical excitation for a series "exotic" closed-shell molecules containing F, Cl, P, Si atoms small radicals, such as CON its variants, were not considered to date investigations. This...
We reexamine ΔCCSD, a state-specific coupled-cluster (CC) with single and double excitations (CCSD) approach that targets excited states through the utilization of non-Aufbau determinants. This methodology is particularly efficient when dealing doubly states, domain in which standard equation-of-motion CCSD (EOM-CCSD) formalism falls short. Our goal here to evaluate effectiveness ΔCCSD applied other types comparing its consistency accuracy EOM-CCSD. To this end, we report benchmark on...
The potential energy curve of the F$_2$ molecule is calculated with Fixed-Node Diffusion Monte Carlo (FN-DMC) using Configuration Interaction (CI)-type trial wavefunctions. To keep number determinants reasonable (the first and second derivatives wavefunction need to be at each step FN-DMC), CI expansion restricted those that contribute most total energy. selection made so-called CIPSI approach (Configuration a Perturbative Selection Iteratively). Quite remarkably, nodes wavefunctions are...
The pair coupled cluster doubles (pCCD) method (where the excitation manifold is restricted to electron pairs) has a series of interesting features. Among others, it provides ground-state energies very close what obtained with doubly occupied configuration interaction (DOCI), but polynomial cost (compared exponential latter). Here, we address whether this similarity holds for excited states by exploring symmetric dissociation linear H
Following the recent work of Eriksen et al. [arXiv:2008.02678], we report performance \textit{Configuration Interaction using a Perturbative Selection made Iteratively} (CIPSI) method on non-relativistic frozen-core correlation energy benzene molecule in cc-pVDZ basis. our usual protocol, obtain $-863.4$ m$E_h$ which agrees with theoretical estimate $-863$ proposed by an extensive array highly-accurate new electronic structure methods.
TREXIO is an open-source file format and library developed for the storage manipulation of data produced by quantum chemistry calculations. It designed with goal providing a reliable efficient method storing exchanging wave function parameters matrix elements, making it important tool researchers in field chemistry. In this work, we present overview library. The consists front-end implemented C programming language two different back-ends: text back-end binary utilizing HDF5 which enables...
All-electron Fixed-node Diffusion Monte Carlo calculations for the nonrelativistic ground-state energy of water molecule at equilibrium geometry are presented. The determinantal part trial wavefunction is obtained from a selected Configuration Interaction calculation [Configuration using Perturbative Selection done Iteratively (CIPSI) method] including up to about 1.4 × 106 determinants. Calculations made cc-pCVnZ family basis sets, with n = 2 5. In contrast most quantum works no...
In diffusion Monte Carlo (DMC) methods, the nodes (or zeroes) of trial wave function dictate magnitude fixed-node (FN) error. standard DMC implementations, are optimized by stochastically optimizing a short multideterminant expansion in presence an explicitly correlated Jastrow factor. Here, following recent proposal, we pursue different route and consider selected configuration interaction (sCI) expansions built with CIPSI (Configuration Interaction using Perturbative Selection made...
We investigate the performance of a class compact and systematically improvable Jastrow-Slater wave functions for efficient accurate computation structural properties, where determinantal component is expanded with perturbatively selected configuration interaction scheme (CIPSI). concurrently optimize molecular ground-state geometry full function-Jastrow factor, orbitals, coefficients-in variational Monte Carlo (VMC) prototypical case 1,3- trans-butadiene, small yet theoretically challenging...
Quantum Monte Carlo (QMC) is a stochastic method that has been particularly successful for ground-state electronic structure calculations but mostly unexplored the computation of excited-state energies. Here, we show within Jastrow-free QMC protocol relying on deterministic and systematic construction nodal surfaces using selected configuration interaction (sCI) expansions, one able to obtain accurate excitation energies at fixed-node diffusion (FN-DMC) level. This evidences errors in ground...
We employ quantum Monte Carlo to obtain chemically accurate vertical and adiabatic excitation energies, equilibrium excited-state structures for the small, yet challenging, formaldehyde thioformaldehyde molecules. A key ingredient is a robust protocol balanced ground- Jastrow-Slater wave functions at given geometry, maintain such description as we relax structure in excited state. use determinantal components generated via selected configuration interaction scheme which targets same...
We report ground- and excited-state dipole moments oscillator strengths (computed in different "gauges" or representations) of full configuration interaction (FCI) quality using the selected method known as Configuration Interaction a Perturbative Selection made Iteratively (CIPSI). Thanks to set encompassing 35 properties computed 11 small molecules, present near-FCI estimates allow us assess accuracy high-order coupled-cluster (CC) calculations including up quadruple excitations. In...
Cyclobutadiene is a well-known playground for theoretical chemists and particularly suitable to test ground- excited-state methods. Indeed, due its high spatial symmetry, especially at the D4h square geometry but also in D2h rectangular arrangement, ground excited states of cyclobutadiene exhibit multiconfigurational characters single-reference methods, such as standard adiabatic time-dependent density-functional theory (TD-DFT) or equation-of-motion coupled cluster (EOM-CC), are notoriously...
We present a comparative study of the spatial distribution spin density ground state CuCl2 using Density Functional Theory (DFT), quantum Monte Carlo (QMC), and post-Hartree-Fock wave function theory (WFT). A number studies have shown that an accurate description electronic structure lowest-lying states this molecule is particularly challenging due to interplay between strong dynamical correlation effects in 3d shell delocalization hole over chlorine atoms. More generally, problem...
We report a universal density-based basis-set incompleteness correction that can be applied to any wave function method. This correction, which appropriately vanishes in the complete (CBS) limit, relies on short-range correlation density functionals (with multideterminant reference) from range-separated density-functional theory (RS-DFT) estimate error. Contrary conventional RS-DFT schemes require an ad hoc range-separation parameter μ, key ingredient here is μ(r) automatically adapts...
By combining extrapolated selected configuration interaction (sCI) energies obtained with the Configuration Interaction using a Perturbative Selection made Iteratively algorithm recently proposed short-range density-functional correction for basis-set incompleteness [E. Giner et al., J. Chem. Phys. 149, 194301 (2018)], we show that one can get chemically accurate vertical and adiabatic excitation with, typically, augmented double-ζ basis sets. We illustrate present approach on various types...