Meanfield calculations
The BerkeleyGW software package uses manybody perturbationtheory formalisms; therefore, one needs to provide a reasonable meanfield starting point for the perturbationtheory calculations. For most application, densityfunctional theory (DFT) based on semilocal functionals provide a good starting point for GW and GWBSE calculations.
The following meanfield codes are currently supported by BerkeleyGW:
In addition, we include a wrapper to convert meanfield quantities to the StochasticGW code.
We provide a library to easily write meanfieldrelated quantities in the format used by BerkeleyGW.
BerkeleyGW requires the following quantities from meanfield codes:
 Meanfield eigenvalues and eigenvectors, stored in
WFN
files, for arbitrary kpoint grids.  The meanfield exchangecorrelation matrix elements,
vxc.dat
, or exchangecorrelation matrix in reciprocal space,VXC
.  Groundstate charge density \rho(G), stored in
RHO
 only for calculations based on the generalized plasmonpole (GPP) model.
For further information on how to use each meanfield code with the appropriate wrapper for BerkeleyGW, we refer to the BerkeleyGW tutorials.
Pitfalls
There are some notorious cases where typical DFT calculations might not provide a good starting point for oneshot perturbationtheory calculations. Examples include:

Germanium crystal, which is often predicted to be metallic at DFT. This issue can be remedied by either using another meanfield starting point, or performing some sort of selfconsistent iteration, for instance, based on the static COHSEX approximation.

Molecules such as silane (SiH4), in which semilocal DFT often yields a LUMO orbital that bound, where in reality it is unbound. These systems can also be remedied by using a different starting meanfield point, or performing selfconsistent GW calculations. For molecules, another common approach is known as best G, best W, where one picks one meanfield starting point to write the Green's function G in \Sigma=iGW, such as HartreeFock, and another one to compute the polarizability \chi^0 used to construct W, such as LDA.

Some strongly correlated systems, especially those with partially filled f orbitals. Systems such as transitionmetal oxides are often tackled with a Hubbardtype of correction scheme, such as DFT+U.