Pros and Cons of the Bethe-Salpeter Formalism for Ground-State Energies

Pierre-François Loos (1) , Anthony Scemama (1) , Ivan Duchemin (2) , Denis Jacquemin (3) , Xavier Blase (4)

1 GMO - Groupe THEO (LCPQ)
2 LSIM - Laboratory of Atomistic Simulation
3 CEISAM - Chimie Et Interdisciplinarité : Synthèse, Analyse, Modélisation
4 NEEL - TMC - Théorie de la Matière Condensée

The combination of the many-body Green's function $GW$ approximation and the Bethe-Salpeter equation (BSE) formalism has shown to be a promising alternative to time-dependent density-functional theory (TD-DFT) for computing vertical transition energies and oscillator strengths in molecular systems. The BSE formalism can also be employed to compute ground-state correlation energies thanks to the adiabatic-connection fluctuation-dissipation theorem (ACFDT). Here, we study the topology of the ground-state potential energy surfaces (PES) of several diatomic molecules near their equilibrium bond length. Thanks to comparisons with state-of-art computational approaches (CC3), we show that ACFDT@BSE is surprisingly accurate, and can even compete with lower-order coupled cluster methods (CC2 and CCSD) in terms of total energies and equilibrium bond distances for the considered systems. However, we sometimes observe unphysical irregularities on the ground-state PES in relation with difficulties in the identification of a few $GW$ quasiparticle energies.

Domaines: Chimie théorique et/ou physique

Pierre-François Loos, Anthony Scemama, Ivan Duchemin, Denis Jacquemin, Xavier Blase. Pros and Cons of the Bethe-Salpeter Formalism for Ground-State Energies. Journal of Physical Chemistry Letters, 2020, 11 (9), pp.3536-3545. ⟨10.1021/acs.jpclett.0c00460⟩. ⟨hal-02475410⟩