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[hal-02157296] Relativistic equation of motion coupled cluster based on four-compoment Hamiltonians (6/18/19)

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[hal-02156152] Line Profiles of the Calcium I Resonance Line in Cool Metal-polluted White Dwarfs (6/16/19)

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[hal-02156091] Distributed Gaussian orbitals for molecular calculations: application to simple systems (6/15/19)

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[hal-02140286] RASPT2 study of the valence excited states of an iron–porphyrin–carbonyl model complex (5/28/19)

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[hal-02129651] Pre-exascale Architectures: OpenPOWER Performance and Usability Assessment for French Scientific Community (6/27/19)

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[hal-02129595] Interaction of Metamitron and Fenhexamid with Ca2+‐ Montmorillonite Clay Surfaces: A Density Functional Theory Molecular Dynamics Study (5/16/19)

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[hal-02088494] Influence of Pseudopotentials on Excitation Energies From Selected Configuration Interaction and Diffusion Monte Carlo (6/14/19)

Quantum Monte Carlo (QMC) methods have been applied very successfully to ground state properties but still remain generally less effective than other non-stochastic methods for electronically excited states. Nonetheless, we have recently reported accurate excitation energies for small organic molecules at the fixed-node diffusion Monte Carlo (FN-DMC) within a Jastrow-free QMC protocol relying on a deterministic and systematic construction of nodal surfaces using the selected configuration interaction (sCI) algorithm known as CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively). Albeit highly accurate, these all-electron calculations are computationally expensive due to the presence of core electrons. One very popular approach to remove these chemically-inert electrons from the QMC simulation is to introduce pseudopotentials. However, such an approach inevitably introduces a bias due to the approximate nature of these pseudopotentials. Furthermore, an additional bias may be introduced in DMC due to the localization of nonlocal pseudopotentials. Taking the water molecule as an example, we investigate the influence of pseudopotentials on vertical excitation energies obtained with sCI and FN-DMC methods. Although pseudopotentials are known to be relatively safe for ground state properties, we evidence that special care is required if one strives for highly accurate vertical transition energies. Indeed, comparing all-electron and valence-only calculations, we show that the approximate nature of the pseudopotentials can induce errors as large as 0.1 eV on the excitation energies. While acceptable for most chemical applications, it might become unacceptable for benchmark studies.

AB-INITIO ALGORITHM Dichroïsme circulaire Clay mineral Ground states Single-core optimization BIOMOLECULAR HOMOCHIRALITY Coupled cluster Quantum Chemistry Car-Parrinello molecular dynamics Acrolein Contact electron density Dynamique Moléculaire Car-Parrinello Pesticides Metabolites Clustering Molecular modeling Environmental fate Partial least squares BENZENE MOLECULE Relativistic quantum chemistry Wave functions Argon Relativistic corrections Pesticide Electron correlation Configuration interactions Beyond Standard Model Cusp Contact density Time-dependent density-functional theory 3115vn Chemical Physics Corrélation et relativité Electron correlations Petascale Chemical-Bonds Dispersion forces Configuration Interaction Chiral oxorhenium CP violation Dispersion coefficients Coupled Cluster Density Functional Theory DENSITY-FUNCTIONAL THEORY Biodegradation Large systems Chiral transition metal complexes CP Violation Coupled cluster calculations Basis sets 3115ag Atrazine-cations complexes 3115am Chiral halogenomethanes Béryllium Conditions aux limites périodiques CLUSTERS Corrélation électronique Perturbation theory Chemical concepts ELECTRONIC-STRUCTURE Aimantation Polarizabilities Excited states 3115vj Range separation Parallel speedup Correlation and relativity DEPENDENT BASIS-SETS Electric and magnetic properties Electric Dipole Moments Ab initio calculation Valence bond Diatomic molecules Carbon Nanotubes Quantum Monte Carlo Chimie quantique Atrazine ENANTIOMERIC MOLECULES CHEMICAL-SHIFTS Coupled cluster theory Atomic and molecular structure and dynamics Spin-orbit interactions Density functional theory Argile Diatomics molecules Anderson mechanism 3115bw 3315Fm 3115ae CIPSI COMPUTATION Parity violation Determinants Circular dichroism Atom AROMATIC-MOLECULES ELECTROWEAK INTERACTIONS Analytic gradient 3115aj 3470+e Atomic data Calcul ab initio AB-INITIO CALCULATION