diff --git a/BSE-PES.tex b/BSE-PES.tex index 384ba56..3ca82fe 100644 --- a/BSE-PES.tex +++ b/BSE-PES.tex @@ -386,14 +386,17 @@ As a final remark, we point out that Eq.~\eqref{eq:EtotBSE} can be easily genera \section{Computational details} \label{sec:comp_details} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -All the preliminary {\GW} calculations performed to obtain the screened Coulomb operator and the quasiparticle energies have been done using a Hartree-Fock (HF) starting point, which is a very adequate choice in the case of the (small) systems that we consider here. +All the preliminary {\GW} calculations performed to obtain the screened Coulomb operator and the quasiparticle energies have been done using a (restricted) Hartree-Fock (HF) starting point, which is a very adequate choice in the case of the (small) systems that we consider here. Dunning's basis sets are defined in cartesian gaussians. Both perturbative {\GW} (or {\GOWO}) \cite{Hybertsen_1985a, Hybertsen_1986} and partially self-consistent {\evGW} \cite{Hybertsen_1986, Shishkin_2007, Blase_2011, Faber_2011} calculations are employed as starting point to compute the BSE neutral excitations. These will be labeled as BSE@{\GOWO} and BSE@{\evGW}, respectively. In the case of {\GOWO}, the quasiparticle energies have been obtained by linearizing the non-linear, frequency-dependent quasiparticle equation. For {\evGW}, the quasiparticle energies are obtained self-consistently and we have used the DIIS convergence accelerator technique proposed by Pulay \cite{Pulay_1980,Pulay_1982} to avoid convergence issues. Further details about our implementation of {\GOWO} and {\evGW} can be found in Refs.~\onlinecite{Loos_2018,Veril_2018}. -Finally, the infinitesimal $\eta$ has been set to $10^{-3}$ for all calculations. +Finally, the infinitesimal $\eta$ has been set to zero for all calculations. +\titou{For sake of comparison, no frozen core approximation. +The numerical integration required to compute the correlation energy along the adiabatic path has been computed with a 21-point Gauss-Legendre quadrature. +This number of points is probably too big...} Because Eq.~\eqref{eq:EcBSE} requires the entire BSE excitation spectrum (both singlet and triplet), we perform a complete diagonalization of the $\Nocc \Nvir \times \Nocc \Nvir$ BSE linear response matrix [see Eq.~\eqref{eq:small-LR}], which corresponds to a $\order{\Nocc^3 \Nvir^3}$ computational cost. This step is, by far, the computational bottleneck in our current implementation. @@ -406,24 +409,39 @@ This step is, by far, the computational bottleneck in our current implementation %%% TABLE I %%% \begin{table*} \caption{ -Equilibrium distances of ground and excited states of diatomic molecules obtained at various levels of theory.} +Equilibrium distances (in bohr) of the ground state of diatomic molecules obtained at various levels of theory and basis sets.} \label{tab:Req} \begin{ruledtabular} \begin{tabular}{llcccccccc} - & & \mc{2}{c}{FCI} & \mc{2}{c}{CC3} & \mc{2}{c}{BSE@{\GOWO}} & \mc{2}{c}{BSE@{\evGW}} \\ - \cline{3-4} \cline{5-6} \cline{7-8} \cline{9-10} - Molecule & State & cc-pVDZ & cc-pVTZ & cc-pVDZ & cc-pVTZ & cc-pVDZ & cc-pVTZ & cc-pVDZ & cc-pVTZ \\ + & & \mc{8}{c}{Molecules} \\ + \cline{3-10} + Method & Basis & \ce{H2} & \ce{LiH} & \ce{LiF}& \ce{N2} & \ce{CO} & \ce{BF} & \ce{F2} & \ce{HCl} \\ \hline - \ce{H2} & $S_0$ & 1.438 & 1.403 & & & 1.440 & & 1.432 & \\ - & $S_2$ & & & & & 1.451 & & 1.442 & \\ - & $S_5$ & & & & & 1.781 & & 1.778 & \\ - \ce{LiH} & & & & \\ - \ce{LiF} & & & & \\ - \ce{HCl} & & & & \\ - \ce{N2} & & & & \\ - \ce{CO} & & & & \\ - \ce{BF} & & & & \\ + CC3 & cc-pVDZ & 1.438 & 3.043 & 3.012 & 2.114 & 2.166 & 2.444 & 2.740 & 2.435 \\ + & cc-pVTZ & 1.403 & 3.011 & 2.961 & 2.079 & 2.143 & 2.392 & 2.669 & 2.413 \\ + & cc-pVQZ & 1.402 & 3.019 & & & & & & \\ + CCSD & cc-pVDZ & & & & & & & & \\ + & cc-pVTZ & & & & & & & & \\ + & cc-pVQZ & & & & & & & & \\ + CC2 & cc-pVDZ & & & & & & & & \\ + & cc-pVTZ & & & & & & & & \\ + & cc-pVQZ & & & & & & & & \\ + MP2 & cc-pVDZ & & & & & & & & \\ + & cc-pVTZ & & & & & & & & \\ + & cc-pVQZ & & & & & & & & \\ + BSE@{\GOWO}@HF & cc-pVDZ & & & & & & & & \\ + & cc-pVTZ & & & & & & & & \\ + & cc-pVQZ & & & & & & & & \\ + RPA@{\GOWO}@HF & cc-pVDZ & & & & & & & & \\ + & cc-pVTZ & & & & & & & & \\ + & cc-pVQZ & & & & & & & & \\ + RPAx@HF & cc-pVDZ & & & & & & & & \\ + & cc-pVTZ & & & & & & & & \\ + & cc-pVQZ & & & & & & & & \\ + RPA@HF & cc-pVDZ & & & & & & & & \\ + & cc-pVTZ & & & & & & & & \\ + & cc-pVQZ & & & & & & & & \\ \end{tabular} \end{ruledtabular} \end{table*}