@article{ISI:000342662600002,
 abstract = {The GW approximation to the electron self-energy has become a standard
method for ab initio calculation of excited-state properties of
condensed-matter systems. In many calculations, the G W self-energy
operator, E, is taken to be diagonal in the density functional theory
(DFT) Kohn-Sham basis within the G0 W0 scheme. However, there are known
situations in which this diagonal Go Wo approximation starting from DFT
is inadequate. We present two schemes to resolve such problems. The
first, which we called sc-COHSEX-PG W, involves construction of an
improved mean field using the static limit of GW, known as COHSEX
(Coulomb hole and screened exchange), which is significantly simpler to
treat than GW W. In this scheme, frequency-dependent self energy E(N),
is constructed and taken to be diagonal in the COHSEX orbitals after the
system is solved self-consistently within this formalism. The second
method is called off diagonal-COHSEX G W (od-COHSEX-PG W). In this
method, one does not self-consistently change the mean-field starting
point but diagonalizes the COHSEX Hamiltonian within the Kohn-Sham basis
to obtain quasiparticle wave functions and uses the resulting orbitals
to construct the G W E in the diagonal form. We apply both methods to a
molecular system, silane, and to two bulk systems, Si and Ge under
pressure. For silane, both methods give good quasiparticle wave
functions and energies. Both methods give good band gaps for bulk
silicon and maintain good agreement with experiment. Further, the
sc-COHSEX-PGW method solves the qualitatively incorrect DFT mean-field
starting point (having a band overlap) in bulk Ge under pressure.},
 article-number = {115148},
 author = {Jain, Manish and Deslippe, Jack and Samsonidze, Georgy and Cohen, Marvin
L. and Chelikowsky, James R. and Louie, Steven G.},
 doi = {10.1103/PhysRevB.90.115148},
 eissn = {1550-235X},
 issn = {1098-0121},
 journal = {PHYSICAL REVIEW B},
 month = {SEP 26},
 number = {11},
 orcid-numbers = {Samsonidze, Georgy/0000-0002-3759-1794
Jain, Manish/0000-0001-9329-6434},
 researcherid-numbers = {Samsonidze, Georgy/G-3613-2016
Jain, Manish/A-8303-2010},
 times-cited = {13},
 title = {Improved quasiparticle wave functions and mean field for G(0)W(0)
calculations: Initialization with the COHSEX operator},
 unique-id = {ISI:000342662600002},
 volume = {90},
 year = {2014}
}