no code implementations • 8 Nov 2018 • Bastien Mussard
The projected oscillator orbitals (pOOs) are localized virtual orbitals constructed by multiplying localized occupied orbitals by harmonics.
Chemical Physics
no code implementations • 30 Sep 2017 • Bastien Mussard, Sandeep Sharma
In this work we demonstrate that the heat bath configuration interaction (HCI) and its semistochastic extension can be used to treat relativistic effects and electron correlation on an equal footing in large active spaces to calculate the low energy spectrum of several systems including halogens group atoms (F, Cl, Br, I), coinage atoms (Cu, Au) and the Neptunyl(VI) dioxide radical.
Chemical Physics
no code implementations • 24 Aug 2017 • James E. T. Smith, Adam A. Holmes, Bastien Mussard, Sandeep Sharma
We use the recently-developed Heat-bath Configuration Interaction (HCI) algorithm as an efficient active-space solver to perform multi-configuration self-consistent field calculations (HCISCF) with large active spaces.
Chemical Physics Strongly Correlated Electrons Computational Physics
no code implementations • 27 May 2017 • Bastien Mussard, Emanuele Coccia, Roland Assaraf, Matt Otten, C. J. Umrigar, Julien Toulouse
We present the extension of variational Monte Carlo (VMC) to the calculation of electronic excitation energies and oscillator strengths using time-dependent linear-response theory.
Chemical Physics Computational Physics
no code implementations • 19 Jul 2016 • Szymon Smiga, Odile Franck, Bastien Mussard, Adam Buksztel, Ireneusz Grabowski, Eleonora Luppi, Julien Toulouse
We introduce an orbital-optimized double-hybrid (DH) scheme using the optimized-effective-potential (OEP) method.
Chemical Physics Computational Physics
no code implementations • 13 Jul 2016 • Bastien Mussard, Julien Toulouse
Results on atoms and molecules show that the fractional-charge errors obtained in RSH are much smaller than in the standard Kohn-Sham (KS) scheme applied with semilocal or hybrid approximations, and also generally smaller than in the standard HF method.
Chemical Physics Computational Physics
no code implementations • 22 Apr 2016 • Bastien Mussard, Dario Rocca, Georg Jansen, Janos Angyan
Starting from the general expression for the ground state correlation energy in the adiabatic connection fluctuation dissipation theorem (ACFDT) framework, it is shown that the dielectric matrix formulation, which is usually applied to calculate the direct random phase approximation (dRPA) correlation energy, can be used for alternative RPA expressions including exchange effects.
Chemical Physics
no code implementations • 23 Feb 2016 • Emanuele Coccia, Bastien Mussard, Marie Labeye, Jérémie Caillat, Richard Taïeb, Julien Toulouse, Eleonora Luppi
We explore the computation of high-harmonic generation spectra by means of Gaussian basis sets in approaches propagating the time-dependent Schr{\"o}dinger equation.
Computational Physics Atomic Physics Chemical Physics
no code implementations • 18 Nov 2015 • Bastien Mussard, Janos Angyan
An approximation to the many-body London dispersion energy in molecular systems is expressed as a functional of the occupied orbitals only.
Chemical Physics
no code implementations • 19 Jun 2015 • Bastien Mussard, Peter Reinhardt, Janos Angyan, Julien Toulouse
We show that range separation greatly improves the accuracy of all RPA variants for these properties.
Chemical Physics
no code implementations • 23 Apr 2015 • E Chermak, Peter Reinhardt, Bastien Mussard, Janos Angyan
Selecting excitations in localized orbitals to calculate long-range correlation contributions to range-separated density-functional theory can reduce the overall computational effort significantly.
Chemical Physics
no code implementations • 1 Mar 2015 • Bastien Mussard, Peter G. Szalay, János G. Ángyán
Analytical forces have been derived in the Lagrangian framework for several random phase approximation (RPA) correlated total energy methods based on the range separated hybrid (RSH) approach, which combines a short-range density functional approximation for the short-range exchange-correlation energy with a Hartree-Fock-type long-range exchange and RPA long-range correlation.
Chemical Physics
no code implementations • 1 Mar 2015 • Bastien Mussard, János G. Ángyán
This study is completed by illustrating the well-known isomorphism between the exchange hole and the square of the dominant localized orbital lying in the space region of the reference point of the exchange hole function.
Chemical Physics
no code implementations • 8 Dec 2014 • Odile Franck, Bastien Mussard, Eleonora Luppi, Julien Toulouse
The strategy of range-separated density-functional theory consists in separating the Coulomb electron-electron interaction into long-range and short-range components, and treating the long-range part by an explicit many-body wave-function method and the short-range part by a density-functional approximation.
Chemical Physics Computational Physics
