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Pierre-Francois Loos 2020-01-29 07:19:25 +01:00
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BSE-PES.tex
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@ -182,7 +182,7 @@
The combined many-body Green's function $GW$ and Bethe-Salpeter equation (BSE) formalisms have shown to be a promising alternative to time-dependent density-functional theory (TD-DFT) in order to compute vertical transition energies of 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 topological features of the ground-state potential energy surfaces (PES) of several diatomic molecules near their equilibrium distance.
Thanks to comparisons with state-of-art computational approaches, we show that ACFDT@BSE is surprisingly accurate, and can even compete with coupled cluster methods in terms of total energies, equilibrium distances or \titou{harmonic vibrational frequencies}.
Thanks to comparisons with state-of-art computational approaches, we show that ACFDT@BSE is surprisingly accurate, and can even compete with coupled cluster methods in terms of total energies and equilibrium bond distances.
However, we sometimes observe unphysical irregularities on the ground-state PES, in relation with the appearance of satellite resonances with a weight similar to that of the $GW$ quasiparticle peak.
\end{abstract}
@ -215,7 +215,7 @@ Here, in analogy to the random-phase approximation (RPA)-type formalisms \cite{F
Embracing this definition, the purpose of the present study is to investigate the quality of ground-state PES near equilibrium obtained within the BSE approach for several diatomic molecules.
The location of the minima on the ground-state PES is of particular interest.
This study is a first preliminary step towards the development of analytical nuclear gradients within the BSE@$GW$ formalism.
Thanks to comparison with both similar and state-of-art computational approaches, we show that the ACFDT@BSE@$GW$ approach is surprisingly accurate, and can even compete with high-order coupled cluster (CC) methods in terms of absolute energies, equilibrium distances or \titou{harmonic vibrational frequencies}.
Thanks to comparison with both similar and state-of-art computational approaches, we show that the ACFDT@BSE@$GW$ approach is surprisingly accurate, and can even compete with high-order coupled cluster (CC) methods in terms of absolute energies and equilibrium distances.
However, we also observe, in some cases, unphysical irregularities on the ground-state PES, which are due to the appearance of a satellite resonance with a weight similar to that of the $GW$ quasiparticle peak. \cite{vanSetten_2015,Maggio_2017,Loos_2018,Veril_2018,Duchemin_2020}
%The paper is organized as follows.
@ -470,10 +470,10 @@ SI stands for singlet instability.
& cc-pVTZ & 1.388 & 3.013 & glitch & 2.408 & 2.065 & 2.114 & glitch & glitch \\
& cc-pVQZ & 1.382 & 3.013 & & & & & & \\
RPAx@HF & cc-pVDZ & 1.428 & 3.040 & 2.998 & 2.424 & 2.077 & 2.130 & 2.417 & SI \\
& cc-pVTZ & 1.395 & 3.003 & 2.971 & 2.400 & <2.050 & 2.110 & <2.420 & \\
& cc-pVTZ & 1.395 & 3.003 & 2.971 & 2.400 & 2.046 & 2.110 & 2.368 & \\
& cc-pVQZ & 1.394 & 3.011 & & & & & & \\
RPA@HF & cc-pVDZ & 1.431 & 3.021 & 2.999 & 2.424 & 2.083 & 2.134 & 2.416 & 2.623 \\
& cc-pVTZ & 1.388 & 2.978 & 2.939 & 2.396 & <2.050 & 2.110 & <2.420 & \\
& cc-pVTZ & 1.388 & 2.978 & 2.939 & 2.396 & 2.045 & 2.110 & 2.362 & \\
& cc-pVQZ & 1.386 & 2.994 & & & & & & \\
% FROZEN CORE VERSION
% Method & Basis & \ce{H2} & \ce{LiH}& \ce{LiF}& \ce{N2} & \ce{CO} & \ce{BF} & \ce{F2} & \ce{HCl}\\
@ -567,7 +567,7 @@ Additional graphs for other basis sets and within the frozen-core approximation
\end{figure*}
%%% %%% %%%
The \ce{F2} molecule is a notoriously difficult case to treat due to the relative weakness of its covalent bond (see Fig.~\ref{fig:PES-F2}).
The \ce{F2} molecule is a notoriously difficult case to treat due to the relative weakness of its covalent bond (see Fig.~\ref{fig:PES-F2}), hence the relatively long equilibrium bond length observed for \ce{F2}.
Similarly to what we have observed for \ce{LiF} and \ce{BF}, there is an irregularities near the minimum of the {\GOWO}-based curves.
However, BSE@{\GOWO}@HF is the closest to the CC3 curve