Epsilon
code input keywords (epsilon.inp
)
Required keywords
Optional keywords
accel_chi_summation_no_full_offload
accel_mtxel_band_block_size [integer]
add_w0_freq
broadening [float]
cell_box_truncation
cell_slab_truncation
cell_wire_truncation
chi_add_fact
chi_eigenvalue_cutoff [float]
chi_summation_algo
cluster_size_subspace_diagonalization [integer]
comm_nonblocking_cyclic
coulomb_truncation_radius [float]
cvfit [array of integers]
degeneracy_check_override
delta_frequency [float]
delta_frequency_step [float]
delta_sfrequency [float]
delta_sfrequency_step [float]
do_rpa
dont_check_norms
dont_keep_fix_buffers
dont_use_hdf5
ec0 [float]
ecdel [float]
ecs [float]
eqp_corrections
ev0 [float]
evdel [float]
evs [float]
fermi_level [float]
fermi_level_absolute
fermi_level_relative
frequency_dependence [integer]
frequency_dependence_method [integer]
frequency_high_cutoff [float]
frequency_low_cutoff [float]
full_chi_conv_log [integer]
fullbz_replace
fullbz_write
gcomm_elements
gcomm_matrix
imaginary_frequency [float]
init_frequency [float]
max_mem_nv_block_algo [float]
mtxel_algo
n_ffts_per_batch [integer]
nbasis_subspace [integer]
nfreq_group [integer]
no_min_fftgrid
number_bands [integer]
number_imaginary_freqs [integer]
number_valence_pools [integer]
nv_block [integer]
occ_broadening [float]
partial_occ_degeneracy_tolerance [float]
plasma_freq [float]
qgrid [array of integers]
read_chi_add
read_chi_maxmem_per_block [float]
restart
sfrequency_high_cutoff [float]
sfrequency_low_cutoff [float]
skip_chi
skip_epsilon
spherical_truncation
stop_after_qpt [integer]
sub_collective_eigen_redistr
subsample
subspace_dont_keep_full_eps_omega0
subspace_use_elpa
use_wfn_hdf5
verbosity [integer]
write_subspace_epsinv
write_vcoul
Keyword documentation
Parameters for fullfrequencydependent calculations
Three methods are available, depending on the value of frequency_dependence_method
:

0: Realaxis formalism with AdlerWiser formula:
 A uniform frequency grid is set up from
init_frequency
(defaults to 0), up tofrequency_low_cutoff
, with a spacing ofdelta_frequency
between two frequencies.  A nonuniform frequency grid is setup from
frequency_low_cutoff
tofrequency_high_cutoff
, where the frequency spacing gets increased bydelta_frequency_step
.
 A uniform frequency grid is set up from

1: Realaxis formalism with spectral method:
 A uniform frequency grid is set up from
init_frequency
(defaults to 0), up tofrequency_low_cutoff
, with a spacing ofdelta_frequency
between two frequencies.  A nonuniform frequency grid is setup from
frequency_low_cutoff
tofrequency_high_cutoff
, where the frequency spacing gets increased bydelta_frequency_step
.  A separate frequency grid is setup for the spectral function. The variables
init_sfrequency
,delta_sfrequency
,delta_sfrequency_step
,sfrequency_low_cutoff
, andsfrequency_high_cutoff
define this grid, in an analogy to the flags used to define the grid for the polarizability matrix.
 A uniform frequency grid is set up from

2: Contourdeformation formalism with AdlerWiser formula (default).
 A uniform frequency grid is set up from
init_frequency
(defaults to 0), up tofrequency_low_cutoff
, with a spacing ofdelta_frequency
between two frequencies.  A frequency grid with
number_imaginary_freqs
is setup on the imag axis.
 A uniform frequency grid is set up from
frequency_dependence_method [integer]
Full frequency dependence method for the polarizability, if frequency_dependence
==2:
 0: Realaxis formalism, AdlerWiser formula.
 1: Realaxis formalism, spectral method (PRB 74, 035101, (2006))
 2: Contourdeformation formalism, AdlerWiser formula.
broadening [float]
Broadening parameter for each val>cond transition. It should correspond to the energy resolution due to kpoint sampling, or a number as small as possible if you have a molecule. The default value is 0.1 for method 0 and 1, and 0.25 for method 2.
init_frequency [float]
Lower bound for the linear frequency grid.
frequency_low_cutoff [float]
Upper bound for the linear frequency grid. For methods 0 and 1, it is also the lower bound for the nonuniform frequency grid. Should be larger than the maximum transition, i.e., the energy difference between the highest conduction band and the lowest valence band. The default is 200 eV for method 0 and 1, and 10 eV for method 2. For method 2, you can increase frequency_low_cutoff if you wish to use the Sigma code and look into QP states deep in occupied manifold or high in the unoccupied manifold.
delta_frequency [float]
Frequency step for fullfrequency integration for the linear grid Should be converged (the smaller, the better). For molecules, delta_frequency should be the same as broadening. Defaults to the value of broadening.
number_imaginary_freqs [integer]
Number of frequencies on the imaginary axis for method 2.
frequency_high_cutoff [float]
Upper limit of the nonuniform frequency grid.
Defaults to 4*frequency_low_cutoff
delta_frequency_step [float]
Increase in the frequency step for the nonuniform frequency grid.
delta_sfrequency [float]
Frequency step for the linear grid for the spectral function method.
Defaults to delta_frequency
.
delta_sfrequency_step [float]
Increase in frequency step for the nonuniform grid for the spectral function method.
Defaults to delta_frequency_step
sfrequency_low_cutoff [float]
Upper bound for the linear grid for the spectral function method
and lower bound for the nonuniform frequency grid.
Defaults to frequency_low_cutoff
sfrequency_high_cutoff [float]
Upper limit of the nonuniform frequency grid for the spectral function method.
Defaults to frequency_low_cutoff
add_w0_freq
In case the frequency grid doesn't start at zero (non default value for init_frequency
), it allows to add the
zero frequency as the grid first value, second value being then the one specified by init_frequency
.
Static subspace approximation
Input parameters controlling the fullfrequency static subspace approximation method.
The method speeds up fullfrequency calculations by expanding the
frequencydependent part of the polarizability in the subspace basis formed by the
lowest eigenvectors of the static polarizability
(see Phys. Rev. B 99, 125128, 2019).
The method is implemented for the case of fullfrequency contourdeformation formalism, i.e.,
frequency_dependence
==2 and frequency_dependence_method
==2.
chi_eigenvalue_cutoff [float]
Activate the static subspace approximation and define the screening threshold for
the eigenvalues of the static polarizability (alias eps_trunc_eigen
).
nbasis_subspace [integer]
Define a maximum fixed number of eigenvectors to be used (recommended). Set for example to 25% of the number of Gvectors employed for the expansion of chi0.
write_subspace_epsinv
Write frequencydependent epsilon matrices in eps0mat[.h5]
and epsmat[.h5]
files using the subspace basis instead of the
full Gvector basis (recommended). This flag need to be specified to use the fullfrequency static subspace approximation in sigma.
subspace_dont_keep_full_eps_omega0
Discharge the output of the full static epsilon matrix in the eps0mat[.h5]
and
epsmat[.h5]
files.
subspace_use_elpa
If ELPA library is linked, specify to use ELPA for the diagonalization of the static polarizability.
dont_keep_fix_buffers
Using comm_nonblocking_cyclic
force the algorithm to use buffers for communication with variable size, mainly used for debugging.
sub_collective_eigen_redistr
Replicate eigenvectors using collective operation in the basis transformation step, performs in general worse than point to point, mainly used for debugging.
cluster_size_subspace_diagonalization [integer]
Allows to control the cluster size when performing the diagonalization with ScaLAPACK. In case there are too many eigenvalues clustered together and the diagonalization fails, try increasing this parameter (default is 250).
GPUs Parameters
Input parameters controlling the execution when running with GPU support.
For the default algorithm (keys ending with _algo
) the hierarchy depends on which programming models are compiled in (OpenACC, OpenMPtarget and/or CPU (threaded or not)):
if all possible implementations have been compiled then the hierarchy is OPENACC_ALGO
> OMP_TARGET_ALGO
> CPU_ALGO
.
mtxel_algo
Controlling which algorithm to use for the GPU offload of the mtxel
kernel calculating transition matrix elements.
Possible values are CPU_ALGO
, OPENACC_ALGO
and OMP_TARGET_ALGO
(See section header for default values).
chi_summation_algo
Controlling which algorithm to use for the GPU offload of the chi_summation
kernel calculating the polarizability.
Possible values are CPU_ALGO
, OPENACC_ALGO
and OMP_TARGET_ALGO
(See section header for default values).
n_ffts_per_batch [integer]
Control how many FFTs to perform simultaneously in the batched mtxel
kernel (Default 20).
If set to 1 the band by band mtxel
kernel will be used, see accel_mtxel_band_block_size
.
accel_mtxel_band_block_size [integer]
Control the inner block size in the band by band mtxel
kernel, the larger the better, but uses more memory (Default 20).
accel_chi_summation_no_full_offload
Avoid offloading the whole gme
matrix elements to GPU to accelerate the preparation step in chi_summation
kernel.
Generally it slows down considerably the execution but uses less memory and it's useful in case the prep
execution fails.
To better control the memory usage also have a look to max_mem_nv_block_algo
.
Scissors operator
Scissors operator (linear fit of the quasiparticle
energy corrections) for the bands in WFN
and WFNq
.
For valenceband energies:
ev_cor = ev_in + evs + evdel * (ev_in  ev0)
For conductionband energies:
ec_cor = ec_in + ecs + ecdel * (ec_in  ec0)
Defaults is zero for all entries, i.e., no scissors corrections.
evs
, ev0
, ecs
, ec0
are in eV.
If you have eqp.dat
and eqp_q.dat
files
this information is ignored in favor of the eigenvalues
in eqp.dat and eqp_q.dat.
One can specify all parameters for scissors operator
in a single line with cvfit evs ev0 evdel ecs ec0 ecdel
evs [float]
ev0 [float]
evdel [float]
ecs [float]
ec0 [float]
ecdel [float]
cvfit [array of integers]
Truncation schemes for the Coulomb potential
Since BerkerleyGW is a planewavebased code, one must truncate the Coulomb potential to avoid spurious interactions between repeated supercells when dealing with systems with reduced dimensionality. Make sure you understand how to setup your meanfield calculation so that the supercell is large enough to perform a truncation of the Coulomb potential.
cell_box_truncation
Truncate the Coulomb potential based on the WignerSeitz cell. This is the recommended truncation for 0D systems.
cell_wire_truncation
Truncation scheme for 1D systems, such as carbon nanotubes. The z direction is assumed to be periodic, and x and y confined.
cell_slab_truncation
Truncation scheme for 2D systems, such as graphene or monolayer MoS2. The z direction is assumed to be confined, and x and y periodic.
spherical_truncation
Truncate the Coulomb potential based on an analytical scheme.
This is ok for quasispherical systems, such as CH4 molecule or C60,
but the cell_box_truncation
is the most general and recommended
scheme. When using spherical truncation, you must also specify the
radius for the truncation in spherical_truncation
.
coulomb_truncation_radius [float]
This specifies the radius of for spherical truncation, in Bohr,
so that the Coulomb potential v(r) is zero for r larger than
these values. This flag is to be used together with spherical_truncation
.
Misc. parameters
epsilon_cutoff [float]
Energy cutoff for the dielectric matrix, in Ry. The dielectric matrix \varepsilon_{GG'} will contain all Gvectors with kinetic energy q+G^2 up to this cutoff.
number_bands [integer]
Total number of bands (valence+conduction) to sum over. Defaults to the number of bands in the WFN file minus 1.
use_wfn_hdf5
Read input wavefunction files in HDF5 format: WFN.h5
instead of WFN
and,
if required, WFNq.h5
instead of WFNq
.
frequency_dependence [integer]
This flags specifies the frequency dependence of the inverse dielectric matrix:
 Set to 0 to compute the static inverse dielectric matrix (default).
 Set to 2 to compute the full frequency dependent inverse dielectric matrix.
 Set to 3 to compute the two frequencies needed for GodbyNeeds GPP model.
plasma_freq [float]
Plasma frequency (eV) needed for the contourdeformation method (i.e.,
frequency_dependence
==2). The exact value
is unimportant, especially if you have enough imaginary frequency points. We
recommend you keep this value fixed at 2 Ry.
imaginary_frequency [float]
For frequency_dependence
==3, the value of the purely imaginary frequency, in eV:
comm_nonblocking_cyclic
Within gcomm_matrix
, employs a nonblocking cyclic communication scheme
overlapping computation and communication in the evaluation of the polarizability
(drastically reduce the time spent in communication for large runs, but require more memory).
full_chi_conv_log [integer]
Logging convergence of the head & tail of polarizability matrix with respect to conduction bands:
 Set to 1 for no convergence test
 Set to 0 for the 5 column format including the extrapolated values (default).
 Set to 1 for the 2 column format, real part only.
 Set to 2 for the 2 column format, real and imaginary parts.
begin qpoints ... end
qx qy qz 1/scale_factor is_q0
scale_factor is for specifying values such as 1/3
is_q0 = 0 for regular, nonzero qvectors (read val WFNs from WFN
)
is_q0 = 1 for a small qvector in semiconductors (read val WFNs from WFNq
)
is_q0 = 2 for a small qvector in metals (read val WFNs from WFN
)
if present the small qvector should be first in the list
You can generate this list with kgrid.x
: just set the shifts to zero and use
same grid numbers as for WFN
. Then replace the zero vector with q0.
In the case of RPA energy calculations (do_rpa
) an additional value
at the end of each qpoint line has to be specified with the weight of the qpoint for the BZ integration,
do_rpa
flag needs to be specified before the begin qpoints
block.
fermi_level [float]
Specify the Fermi level (in eV), if you want implicit doping
Note that value refers to energies after scissor shift or eqp corrections.
See also fermi_level_absolute
and fermi_level_relative
to control
the meaning of the Fermi level.
The Fermi level in keyword fermi_level
can be treated as an absolute
value or relative to that found from the mean field (default). Using
fermi_level_absolute
will force the code to recompute the Fermi level
regardless of existing occupations/ifmax array.
fermi_level_absolute
fermi_level_relative
dont_use_hdf5
Read from traditional simple binary format for epsmat/eps0mat instead of HDF5 file format. Relevant only if code is compiled with HDF5 support.
verbosity [integer]
Verbosity level, options are:
 1: default
 2: medium  info about kpoints, symmetries, and eqp corrections.
 3: high  full dump of the reduced and unfolded kpoints.
 4: log  log of various function calls. Use to debug code.
 5: debug  extra debug statements. Use to debug code.
 6: max  only use if instructed to, severe performance downgrade. Note that verbosity levels are cumulative. Most users will want to stick with level 1 and, at most, level 3. Only use level 4+ if debugging the code.
eqp_corrections
Set this to use eigenvalues in eqp.dat and eqp_q.dat If not set, these files will be ignored.
write_vcoul
Write the bare Coulomb potential v(q+G) to file
Matrix Element Communication Method (Chi Sum Comm). Default is gcomm_matrix
which is good if nk, nc, nv > nmtx, nfreq. If nk, nc, nv < nfreq, nmtx
(nk, nv < nfreq since nc \sim nmtx), use gcomm_elements. Only gcomm_elements
is supported with the spectral method.
gcomm_matrix
gcomm_elements
number_valence_pools [integer]
Number of pools for distribution of valence bands The default is chosen to minimize memory in calculation
By default, the code computes the polarizability matrix, constructs the dielectric matrix, inverts it and writes the result to file epsmat. Use keyword skip_epsilon to compute the polarizability matrix and write it to file chimat. Use keyword skip_chi to read the polarizability matrix from file chimat, construct the dielectric matrix, invert it and write the result to file epsmat.
skip_epsilon
skip_chi
stop_after_qpt [integer]
Allows to stop the epsilon calculation after the specified number of qpoints are calculated (default 1, meaning all qpoints calculated).
read_chi_add
Read in screening files (chimat and chi0mat) for system outside of the electronic system
in your current calculation to add to the electronic polarizability you calculate.
For example, you could include the fluid polarizability from the JDFTx computational package,
or the electronic polarizabilities for the substrate for your electronic system that you
calculated previously. Works only with hdf5 and you have to have the following files in your directory:
chi0mat_add.h5
and chimat_add.h5
(only the latter if you are working on a metallic system).
chi_add_fact
If reading in additional screening files, you can scale the readin polarizability by this factor. Default is 1.0.
read_chi_maxmem_per_block [float]
When using skip_chi
allows to control the max memory (in Mb) to use when reading in
block of columns of chimat in h5 format.
nv_block [integer]
Input parameters to activate the valence bands blocked algorithm. Particularly useful in case of memory issues,
the entire epsilon computation is broken into blocks of valence bands, and block size can be given in input such
that memory limit is not exceeded in the allocation of the matrix elements array (pol%gme
). You can either specify
the block size (nv_block
) or the max memory (in Gb) available per MPI task (max_mem_nv_block_algo
).
max_mem_nv_block_algo [float]
nfreq_group [integer]
(Full Frequency only) Calculates several frequencies in parallel. No "new"
processors are used here, the chi summation is simply done in another order
way to decrease communication. This also allows the inversion of multiple
dielectric matrices simultaneously via ScaLAPACK, circumventing ScaLAPACK's
scaling problems. Can be very efficient for system with lots of Gvectors and when
you have many frequencies. In general gives speedup. However, in order to
calculate N frequencies in parallel, the memory to store pol%gme
is currently
multiplied by N as well.
partial_occ_degeneracy_tolerance [float]
Allows to define the threshold for determine the degeneracy between partially occupied valence and conduction eigenvalues in the computation of transition matrix elements (default 1.0E6).
do_rpa
Enable the calculation of the RPA energy.
IMPORTANT NOTES:
(1) Works only in combination with Contourdeformation formalism with or without subspace approximation.
(2) The flag has to be specified before the begin qpoints
block, additionally an extra value at the end of
each qpoint line has to be specified with the weight of the qpoint for the BZ integration.
(3) The imaginary frequency grid will be different than the one used in the standard GW Contourdeformation calculation
so if the eps0mat[.h5]
and epsmat[.h5]
files will be used for a subsequent sigma calculation the calculated eqp
will be different.
'unfolded BZ' is from the kpoints in the WFN file 'full BZ' is generated from the kgrid parameters in the WFN file See comments in Common/checkbz.f90 for more details
fullbz_replace
Replace unfolded BZ with full BZ
fullbz_write
Write unfolded BZ and full BZ to files
degeneracy_check_override
The requested number of bands cannot break degenerate subspace Use the following keyword to suppress this check Note that you must still provide one more band in wavefunction file in order to assess degeneracy Automatically enabled if pseudobands are detected.
no_min_fftgrid
Instead of using the RHO FFT box to perform convolutions, we automatically determine (and use) the smallest box that is compatible with your epsilon cutoff. This also reduces the amount of memory needed for the FFTs. Although this optimization is safe, you can disable it by uncommenting the following line:
restart
Use this flag if you would like to restart your Epsilon calculation instead of starting it from scratch. Note that we can only reuse qpoints that were fully calculated. This flag is ignored unless you are running the code with HDF5.
qgrid [array of integers]
Qgrid for the epsmat file. Defaults to the WFN kgrid.
subsample
Use this option to generate an eps0mat file suitable for subsampled Sigma calculations. The only thing this flag does is to allow a calculation with more than one q\rightarrow0 points without complaining.
dont_check_norms
Whether we want to check WFN norms. Automatically enabled if pseudobands are detected.
occ_broadening [float]
Apply the first order MethfesselPaxton smearing scheme to the band occupations. Note that this keyword must be used with fermi_level_absolute.