density matrix for molecules*

The GW approximation is well known for the calculation of high-quality ionization potentials and electron affinities in solids and molecules. However, the Green's function contains much more information than the mere quasiparticle energies.

Most interestingly, an approximate density matrix can be obtained from the contraction of the GW Green's function. Here we test and assess the quality of this so-called linearized GW density matrix for several molecular properties. We show it is reliable to evaluate the total energy out of a non-self-consistent GW calculation, being an alternative to the famous RPA total energy expression.

Based on a comprehensive benchmark of 34 molecules, we compare the quality of the ionization potential [1] electronic density, Hartree energy, exchange energy, and the Fock operator expectation values [2] against other well-established quantum chemistry techniques. In particular, we show that the obtained linearized GW densities markedly differ from those calculated within the wide-spread quasiparticle self-consistent GW approximation.


[1] F. Bruneval, Phys. Rev. B 99, 041118(R) (2019).
[2] F. Bruneval, J. Chem. Theory Comput. 15, 4069 (2019).