Paratec code
Paratec is a simple DFT code optimized for small and mediumsized systems, and with a tight integration with BerkeleyGW. Please, refer to the full documentation for PARATEC 5.1.12.
Wrapper
PARATEC output for BerkeleyGW is controlled by flags
gw_shift
, gwc
, gwr
, gwscreening
, gwcscreening
, and vxc_matrix_elements
.
The flags can be combined with an underscore: e.g. output_flags gwr_gwscreening
gwr
and gwc
are incompatible; gwscreening
and gwcscreening
are incompatible.
Main flags:

gw_shift q1 q2 q3
Generates qshifted grid, qvector is in crystal coordinates in units of reciprocal lattice vectors (for
WFNq
,WFNq_fi
) This variable does the same job as thekgrid.x
utility. 
output_flags gwc
Writes complex wavefunctions in Gspace, for systems without inversion symmetry about the origin, to file
WFN
(for all codes). 
output_flags gwr
Writes real wavefunctions in Gspace, for systems with inversion symmetry about the origin, to file
WFN
(for all codes) 
output_flags gwscreening
Writes charge density in Gspace to file
RHO
, exchangecorrelation potential in Gspace to fileVXC
, and matrix elements of exchangecorrelation potential to filevxc.dat
(for Sigma). Real if possible andgwc
not set, else complex. 
output_flags gwcscreening
Like
gwscreening
, except forces complex even if real is possible. 
vxc_matrix_elements diagmin diagmax offdiagmin offdiagmax
Specifies the range of bands for which to compute diagonal and offdiagonal matrix elements of exchangecorrelation potential (for Sigma, in conjunction with output_flags gwscreening)
Other key input flags:

pw_job {scf, nonselfcon}
Use scf for initial calculation, nonselfcon for generating BerkeleyGW outputs. (bandstructure does not seem to work)

energy_cutoff ecut
Planewave cutoff for wavefunctions, in Ry.

number_kpoints
 set to 0 to use k_grid and reduce with symmetries
 set to 1 to use k_grid and do not reduce with symmetries
 set to any other number to read from file KPOINTS

k_grid nx ny nz
3 integers specifying MonkhorstPack kgrid dimensions

k_grid_shift dx dy dz
MonkhorstPack kgrid shifts (typically 0.0 or 0.5)

number_bands nb
Number of bands to use in calculation. Fraction actually useful or written to BerkeleyGW output determined by next variable.

eigspacefrac frac
Fraction of bands to converge. Setting a higher number_bands and lower eigspacefrac can make the calculation more efficient depending on the diagonalization scheme. 0 < frac <= 1.0.
You can find the actual input files for PARATEC and BerkeleyGW in
examples/DFT
, in PARATEC subdirectories for each example.
There are also bgw2para
and rho2cd
utilities that convert
BerkeleyGW files WFN
and RHO
to PARATEC format. This may be
useful, for example, if one generates the plane waves on top of the
valence and conduction bands (look into SAPO for details)
and wants to diagonalize them further in PARATEC. There are no input
files; bgw2para
takes as argument the wfn filename,
and it creates files WFN$n.$s
and BAND
needed for PARATEC
.
Similarly, rho2cd
requires file RHO
and it creates file CD
.
Utilities
kptlist.pl
Extracts a formatted list of kpoints from PARATEC file for use in the Sigma code
qptlist.pl
Extracts a formatted list of qpoints from PARATEC file for use in the Epsilon code
Additional information
To build with support for BerkeleyGW output, in arch.mk
set the
line GWWFNPATH
to BerkeleyGW/library
, and add DBGW
to M4OPTLIBS
.
Literature:
 B. G. Pfrommer, J. Demmel, and H. Simon, "Unconstrained Energy Functionals for Electronic Structure Calculations," J. Comp. Phys. 150, 287 (1999).
 B. G. Pfrommer, M. Cote, S. G. Louie, and M. L. Cohen, "Relaxation of Crystals with the QuasiNewton Method," J. Comp. Phys. 131, 233 (1997).
 Mathieu Taillefumier, Delphine Cabaret, AnneMarie Flank, and Francesco Mauri, "Xray absorption nearedge structure calculations with pseudopotentials: Application to the Kedge in diamond and alphaquartz," Phys. Rev. B 66, 195107 (2002).
 http://cmsn.drupalgardens.com/sites/cmsn.drupalgardens.com/files/CMSN_Newsletter_Vol2No2.pdf
The pseudopotentials for PARATEC can be generated with the fhi98PP
program
which is available for download at
http://www.fhiberlin.mpg.de/th/fhi98md/fhi98PP/