TABLE OF CONTENTS
INTRODUCTION
&ENVIRON
environ_type  verbose  environ_restart  oldenviron  environ_thr  environ_nskip  system_ntyp  system_dim  system_axis  env_electrostatic  env_static_permittivity  env_optical_permittivity  env_surface_tension  env_pressure  env_external_charges  env_dielectric_regions  env_electrolyte_ntyp  stern_entropy  cion  cionmax  rion  zion  solvent_temperature  add_jellium  atomicspread
&BOUNDARY
solvent_mode  rhomax  rhomin  tbeta  alpha  softness  solvent_distance  solvent_spread  stern_mode  stern_rhomax  stern_rhomin  stern_tbeta  stern_alpha  stern_softness  stern_distance  stern_spread  stype  radius_mode  solvationrad  corespread  solvent_radius  radial_scale  radial_spread  filling_threshold  filling_spread  boundary_core  ifdtype  nfdpoint
&ELECTROSTATIC
problem  solver  auxiliary  tol  mix  pbc_dim  pbc_axis  pbc_correction
EXTERNAL_CHARGES
Q  x  y  z  spread  dim  axis
DIELECTRIC_REGIONS
EpsSt  EpsOpt  x  y  z  width  spread  dim  axis
INTRODUCTION
Input data format: { } = optional, [ ] = it depends,  = or
All quantities whose dimensions are not explicitly specified are in
RYDBERG ATOMIC UNITS. Charge is "number" charge (i.e. not multiplied
by e); potentials are in energy units (i.e. they are multiplied by e).
BEWARE: TABS, DOS <CR><LF> CHARACTERS ARE POTENTIAL SOURCES OF TROUBLE
Comment lines in namelists can be introduced by a "!", exactly as in fortran
code. Comments lines in cards can be introduced by either a "!" or a "#"
character in the first position of a line.
Do not start any line in cards with a "/" character.
Structure of the environ.in input file:
===============================================================================
&ENVIRON
...
/
[ &BOUNDARY
...
/ ]
[ &ELECTROSTATIC
...
/ ]
[ EXTERNAL_CHARGES { bohr  angstrom }
Q1 0.0 0.0 0.0 { spread_Q1 dim_Q1 axis_Q1 }
Q2 0.5 0.0 0.0 { spread_Q2 dim_Q2 axis_Q2 } ]
[ DIELECTRIC_REGIONS { bohr  angstrom }
EPSst_E1 EPSopt_E1 0.0 0.0 0.0 width_E1 { spread_E1 dim_E1 axis_E1 }
EPSst_E2 EPSopt_E2 0.0 0.0 0.0 width_E2 { spread_E2 dim_E2 axis_E2 } ]
Namelist: &ENVIRON

This namelist is always needed !
environ_type 
CHARACTER 
Default: 
'input'

Status: 
OPTIONAL

Set up all of the environment embedding flags and interface
parameters according to predefined types:
'input':
Do not use predefined types, read the flags of the different contribution from input
or use the defauls values (which correspond to no contributions).
'vacuum':
All environment embeddings are turned off, but pbc corrections, external charges and
electrolyte charges can be present.
'water':
Set up the main physical constants to the experimental values for water at room temperature
( env_static_permittivity = 78.3 ). Set the tunable embedding flags to the values optimized
to reproduce aqueous solvation of small neutral organic compounds, corresponding to
nonelectrostatic contributions modelled via pressure ( env_pressure = 0.35 GPa )
and surface tension ( env_surface_tension = 50 dyn/cm ) effects (see references below).
For electronsdependent interfaces (selfconsistent continuum solvation, SCCS), set soft
interface parameters to the optimal values ( rhomax = 0.005; rhomin = 0.0001)
derived in O. Andreussi, I. Dabo and N. Marzari, J. Chem. Phys. 136 064102 (2012).
For ionsdependent interfaces (softsphere continuum solvation, SSCS), set rigid
interface parameter to the optimal value ( alpha = 1.12 ) derived in
G. Fisicaro et al. J. Chem. Theory Comput. 13, 8, 3829 (2017).
'watercation':
Set up the main physical constants to the experimental values for water at room temperature
( env_static_permittivity = 78.3 ). Set the tunable embedding flags to the values optimized
to reproduce aqueous solvation of small organic cations.
SCCS parameters ( env_pressure = 0.125 GPa; env_surface_tension = 5.0 dyn/cm;
rhomax = 0.0035; rhomin = 0.0002 ) were derived in C. Dupont, O. Andreussi and
N. Marzari, J. Chem. Phys. 139, 214110 (2013)
SSCS parameters ( env_pressure = 0.35 GPa; env_surface_tension = 50.0 dyn/cm;
alpha = 1.10 ) were derived in G. Fisicaro et al. J. Chem. Theory Comput.
13, 8, 3829 (2017).
'wateranion':
Set up the main physical constants to the experimental values for water at room temperature
( env_static_permittivity = 78.3 ). Set the tunable embedding flags to the values optimized
to reproduce aqueous solvation of small organic cations.
SCCS parameters ( env_pressure = 0.45 GPa; env_surface_tension = 0.0 dyn/cm;
rhomax = 0.0155; rhomin = 0.0024 ) were derived in C. Dupont, O. Andreussi and
N. Marzari, J. Chem. Phys. 139, 214110 (2013)
SSCS parameters ( env_pressure = 0.35 GPa; env_surface_tension = 50.0 dyn/cm;
alpha = 0.98 ) were derived in G. Fisicaro et al. J. Chem. Theory Comput.
13, 8, 3829 (2017).

verbose 
INTEGER 
Default: 
0

Status: 
OPTIONAL

Control the amount of output written to specific output files, mostly useful for debugging purposes
verbose .EQ. 0 minimal information written to standard output
verbose .EQ. 1 additional information written to environ.debug file
verbose .EQ. 2 dumping of main physical quantities on the realspace grid in the form of
*.cube files
verbose .GE. 3 dumping of several intermediate physical quantites on the realspace grid
as this is done at every SCF step it will slow down the calculation significantly

environ_restart 
LOGICAL 
Default: 
.false.

Status: 
OPTIONAL

Compute environ contributions during the initialization step, useful for 'restart' calculations
and systems with a goodenough initial guess

oldenviron 
LOGICAL 
Default: 
.false.

Status: 
OPTIONAL

Use some legacy code in order to compare with results from Environ v0.2

environ_thr 
REAL 
Default: 
1.d1

Status: 
IMPORTANT. The default value is only valid for small systems, while is too conservative for larger systems

Only include/update environment contributions when SCF accuracy is below this threshold.
Since the environment region is defined in terms of the electronic density, the test is done
in order to avoid computing unphysical environment contributions, usually to skip the
environ calculation during the first couple of SCF step.
IMPORTANT: as the SCF accuracy is an extensive property (increases with the number of electrons in
the system), the optimal environ_thr will also vary with system size.

environ_nskip 
INTEGER 
Default: 
1

Only include/update environment contributions after the first environ_nskip steps of CP dynamics.

system_ntyp 
INTEGER 
Default: 
0

Specify the atom types that are used to determine the origin and size of the embedded system,
for systemdependent properties in Environ (e.g. see later systemdependent boundary)
Atom types up to system_ntyp are used, all atoms are used by default or if system_ntyp == 0.

system_dim 
INTEGER 
Default: 
0

Dimensionality of the embedded system, used to determine size (only ortogonally to periodic
dimensions) and position (0 = 0D, 1 = 1D, 2 = 2D).

system_axis 
INTEGER 
Default: 
3

Main axis of the embedded system, only necessary for partially periodic systems
(1 = x, 2 = y, 3 = z).

env_electrostatic 
LOGICAL 
Default: 
.false.

Status: 
REQUIRED

Generic keyword that flags the need to read the &ELECTROSTATIC namelist. Any electrostatic
embedding keyword (env_static_permittivity, env_electrolyte_ntyp) will turn this keyword on.
One needs to turn on explicitly this keyword to activate electrostatic embedding effects
that do not have a specific activation keyword, such as for PBC correction schemes.

env_static_permittivity 
REAL 
Default: 
1.D0

Status: 
REQUIRED

Static dielectric permittivity of the elctrostatic continuum embedding model.
This keyword (like all the env_* keywords) is also the flag which controls the activation
of the specific contribution: if set equal to one (=vacuum) no dielectric effects from the environment.

env_optical_permittivity 
REAL 
Default: 
1.D0

Status: 
REQUIRED

Optical dielectric permittivity of the electrostatic continuum embedding model,
only needed for TDDFPT calculations. If set equal to one (=vacuum) no dielectric
effects in linear response calculations.

env_surface_tension 
REAL 
Default: 
0.D0

Status: 
REQUIRED

Surface tension (gamma) of the environment in CGS units dyn/cm.
This keyword controls the activation of the surfacedependent contribution to
the solute's Hamiltonian (gamma*S): if set equal to 0.D0 no surface
contribution from the environment.
This contribution may be straighforwardly used to compute cavitation free energies,
as proposed by Scherlis et al. in J. Chem. Phys. 124, 074103 (2006).
NOTE that the current implementation uses an improved definition of the
quantumsurface O. Andreussi, I. Dabo and N. Marzari, J. Chem. Phys. 136 064102 (2012).
This contribution can also be used as a simplified approach to the more general
nonelectrostatic contributions to solvation, as in the SCCS approach.
In this second case, env_surface_tension needs not to correspond to the
real surface tension of the solvent, but is used as a fitting parameter.
See O. Andreussi, I. Dabo and N. Marzari, J. Chem. Phys. 136 064102 (2012)

env_pressure 
REAL 
Default: 
0.D0

Status: 
REQUIRED

External pressure (P) of the environment in GPa.
This keyword controls the activation of the volumedependet contribution to
the solute's Hamiltonian (P*V): if set equal to 0.D0 no volume contribution
from the environment.
This contribution may be straightforwardly used to compute the electronic entalpy,
i.e. to model finite systems under pressure, as proposed by M. Cococcioni et al. in
Phys. Rev. Lett. 94, 145501 (2005). This contribution can also be used as a simplified
approach to more complex and general nonelectrostatic contributions to solvation,
as in the SCCS approach. In this second case, env_pressure needs not correspond to the
real external pressure of the environment, but is used as a fitting parameter
(and can assume negative values). See O. Andreussi, I. Dabo and N. Marzari,
J. Chem. Phys. 136 064102 (2012)

env_external_charges 
INTEGER 
Default: 
0

Status: 
REQUIRED

Number of fixed external charges. This keyword controls how many fixed external densities of charge need to be
included in the simulation box. Shape, position and amount of charge of each external density need to be specified
in the EXTERNAL_CHARGES card.

env_dielectric_regions 
INTEGER 
Default: 
0

Status: 
REQUIRED

Number of fixed dielectric regions. This keyword controls how many regions of fixed permittivities (static and optical)
need to be included in the simulation box. Shape, position and permittivities of each region need to be specified
in the DIELECTRIC_REGIONS card.

env_electrolyte_ntyp 
INTEGER 
Default: 
0

Status: 
REQUIRED

Number countercharge species to be added in the continuum region modelling the electrolyte (if different
from zero, must be greater or equal to 2, in order for the electrolyte to be charge neutral).

stern_entropy 
CHARACTER 
Default: 
'full'

Status: 
OPTIONAL

Keyword to set the electrolyte entropy terms that are affected by the Sternlayer correction.
'ions' : only ionic terms ( Ringe et al. J. Chem. Theory Comput. 12, 4052 ).
'full' : all terms ( Dabo et al. arXiv 0901.0096 ).

cion(i), i=1,env_electrolyte_ntyp 
REAL 
Default: 
1.0

Status: 
OPTIONAL

Molar concentration of ionic countercharge (in mol/L).

cionmax 
REAL 
Default: 
0.D0

Status: 
OPTIONAL

Maximum molar concentration of ionic countercharge (in mol/L).

rion 
REAL 
Default: 
0.D0

Status: 
OPTIONAL

Mean atomic radius of ionic countercharge (a.u.).

zion(i), i=1,env_electrolyte_ntyp 
REAL 
Default: 
1.0

Status: 
OPTIONAL

Valence of ionic countercharge.

solvent_temperature 
REAL 
Default: 
300.0

Status: 
OPTIONAL

Temperature of electrolyte solution, needed by PoissonBoltzmann equation.

add_jellium 
LOGICAL 
Default: 
.FALSE.

Status: 
OBSOLETE

Control if jellium polarization is included in the calculation of dielectric environment effects on
charged solutes. The jellium contribution, although it formally needs to be considered, is a PBC
artifact and needs to be removed when applying periodic boundary correction schemes. Thus, in any
reasonable simulation there is no need to explicitly include the jellium contribution.

atomicspread(i), i=1,ntyp 
REAL 
Default: 
0.5

Status: 
OPTIONAL

In the calculation of electrostatic contributions, ionic charge densities are modelled
as gaussians of fixed spread, as specified by atomicspread(ityp) for each atomic type.
Results are identical to using pointlike charges (as is usually done in PW), unless the gaussian
spreads are too large. The default value of 0.5 a.u. was derived to be safe enough in most
common atom types. A too small value may require larger density cutoffs (ecutrho).



Namelist: &BOUNDARY

This namelist is not needed if there are no embedding schemes requiring a continuum interface
solvent_mode 
CHARACTER 
Default: 
'electronic'

Status: 
REQUIRED

Choice of the interface function representing the boundary between the
QM region and the solvent embedding environment. Dielectric, surface and
volume embedding will all act on the solvent interface (as opposed to
the electrolyte embedding that will act on the electrolyte interface).
'electronic':
interface depends selfconsist. on electronic density, corresponds
to the Selfconsistent Continuum Solvation approach (SCCS).
'ionic':
interface defined on atomic positions, corresponds to the
Softsphere Continuum Solvation approach (SSCS).
'full':
similar to electronic, but an extra density is added to
represent the core electrons and the nuclei. This extra
density is defined as the sum of gaussian functions centered
on atomic positions of width specified by the corespread(ityp) keyword.
'system':
inteface defined as a simple analytical function of system position and
dimensionality.

rhomax 
REAL 
Default: 
0.005

Status: 
OPTIONAL

First parameter of the densitydependent interface function,
roughly corresponding to the density threshold of the continuum model.

rhomin 
REAL 
Default: 
0.0001

Status: 
OPTIONAL

Second parameter of the densitydependent interface function, when stype=1.

tbeta 
REAL 
Default: 
4.8

Status: 
OPTIONAL

Second parameter of the densitydependent interface function, when stype=0.

alpha 
REAL 
Default: 
1.0

Status: 
OPTIONAL

Main parameter of ionsdependent interface function, corresponding to the homogeneous
scaling factor of ionic radii (specified by the radius_mode keyword or by solvationrad(ntyp)).

softness 
REAL 
Default: 
0.5

Status: 
OPTIONAL

Numerical spread of the softsphere functions used for the ionsdependent interfaces.

solvent_distance 
REAL 
Default: 
1.0

Status: 
OPTIONAL

Distance of the systemdependent interface from the center of the system, computed as the
center of ionic charge of the atomic types entering the definition of the system
(as specified in the system_ntyp keyword of the &ENVIRON namelist).

solvent_spread 
REAL 
Default: 
0.5

Status: 
OPTIONAL

Numerical spread of the analytical function used for the systemdependent interface.

stern_mode 
CHARACTER 
Default: 
'electronic'

Status: 
REQUIRED

Choice of the interface function representing the boundary between the
QM region and the electrolyte embedding environment. Please note that a
separate set of keywords is used to specify the parameters of the electrolyte
interface function (all exploiting the stern_ prefix).
'electronic':
interface depends selfconsist. on electronic density, corresponds
to the Selfconsistent Continuum Solvation approach (SCCS).
'ionic':
interface defined on atomic positions, corresponds to the
Softsphere Continuum Solvation approach (SSCS).
'full':
similar to electronic, but an extra density is added to
represent the core electrons and the nuclei. This extra
density is defined as the sum of gaussian functions centered
on atomic positions of width specified by the corespread(ityp) keyword.
'system':
inteface defined as a simple analytical function of system position and
dimensionality.

stern_rhomax 
REAL 
Default: 
0.005

Status: 
OPTIONAL

First parameter of the densitydependent interface function,
roughly corresponding to the density threshold of the continuum model.
Used for the electrolyte interface.

stern_rhomin 
REAL 
Default: 
0.0001

Status: 
OPTIONAL

Second parameter of the densitydependent interface function, when stype=1.
Used for the electrolyte interface.

stern_tbeta 
REAL 
Default: 
4.8

Status: 
OPTIONAL

Second parameter of the densitydependent interface function, when stype=0
Used for the electrolyte interface.

stern_alpha 
REAL 
Default: 
1.0

Status: 
OPTIONAL

Main parameter of ionsdependent interface function, corresponding to the homogeneous
scaling factor of ionic radii (specified by the radius_mode keyword or by solvationrad(ntyp)).
Used for the electrolyte interface.

stern_softness 
REAL 
Default: 
0.5

Status: 
OPTIONAL

Numerical spread of the softsphere functions used for the ionsdependent interfaces.
Used for the electrolyte interface.

stern_distance 
REAL 
Default: 
1.0

Status: 
OPTIONAL

Distance of the systemdependent interface from the center of the system, computed as the
center of ionic charge of the atomic types entering the definition of the system
(as specified in the system_ntyp keyword of the &ENVIRON namelist).
Used for the electrolyte interface.

stern_spread 
REAL 
Default: 
0.5

Status: 
OPTIONAL

Numerical spread of the analytical function used for the systemdependent interface.
Used for the electrolyte interface.

stype 
INTEGER 
Default: 
1

Status: 
OPTIONAL

The shape of the environment region is defined according to a specific switching function of the electronic
density:
stype .EQ. 0 : Original switching function from Fattebert and Gygi.
Requires two parameters: rhomax and tbeta
stype .EQ. 1 : Optimally smooth switching function from the SCCS method, redefined for the nonelectrostatic part.
Requires two parameters: rhomax and rhomin
stype .EQ. 2 : Optimally smooth switching function from the SCCS method of Andreussi et al.
Requires two parameters: rhomax and rhomin

radius_mode 
CHARACTER 
Default: 
'uff'

Status: 
OPTIONAL

Specify the predefined set of atomic radii to be used when building an ionsdependent interface.
'pauling' : R.C. Weast, ed., Handbook of chemistry and physics (CRC Press, Cleveland, 1981)
'bondi' : A. Bondi, J. Phys. Chem. 68, 441 (1964)
'uff' : A.K. Rapp/'{e} et al. J. Am. Chem. Soc. 114(25) pp.1002410035 (1992)

solvationrad(i), i=1,ntyp 
REAL 
Default: 
3.0

Status: 
OPTIONAL

Atomic radii used for the ionsdependent interface as introduced by G. Fisicaro et al.
J. Chem. Theory Comput. 13, 8, 3829 (2017). These values will overwrite the defaults
set by the radius_mode keyword.

corespread(i), i=1,ntyp 
REAL 
Default: 
0.5

Status: 
OPTIONAL

Numerical spread of the atomiccentered Gaussian functions used to model core electrons and
ions for interfaces defined on the full set of degrees of freedom of the QM system (iterface mode = full).
NOTE: this numerical parameter should only be used to avoid artefacts coming from the missing
core electrons, if this parameter affects the final results a WARNING will be issued and a smaller
(even null) value should be used instead.

solvent_radius 
REAL 
Default: 
0.0

Status: 
OPTIONAL

Size of the solvent molecules, used in the solventaware algorithm to decide whether to fill a continuum
void or not. If set equal to 0.D0, use the standard local algorithm.

radial_scale 
REAL 
Default: 
2.0

Status: 
OPTIONAL

For solventaware interfaces, compute the filled fraction on a spherical volume whose radius is
radial_scale * solvent_radius. The deafaul value of 2.0 guarantees that spherical voids of the size
of a solvent molecule will be homogenously filled. Larger values will let the algorithm sample a
larger volume of space, increasing the nonlocality of the algorithm.

radial_spread 
REAL 
Default: 
0.5

Status: 
OPTIONAL

For solventaware interfaces, numerical spread of the step function used to compute the filled fraction.

filling_threshold 
REAL 
Default: 
0.825

Status: 
OPTIONAL

For solventaware interfaces, threshold of filledfraction used to decide whether to fill or not
a continuum void. The default value of 7/8 correspond to the geometrical condition required to
homogenously fill a spherical void of radius smaller than the solvent radius.

filling_spread 
REAL 
Default: 
0.02

Status: 
OPTIONAL

For solventaware interfaces, numerical spread of the switching function used to decide whether the
continuum void should be filled or not.

boundary_core 
CHARACTER 
Default: 
'analytic'

Status: 
OPTIONAL

Specify the numerical approach used to compute derivatives of the continuum interface with respect
to realspace coordinates or QM degrees of freedom.
'fft' : fast Fourier transform
'fd' : finite differences in realspace
'analytic' : analytic derivatives for as much as possible (and FFTs for the rest)
NOTE: analytic derivatives, especially for ionsdependent interfaces, may require a large amount of storage.
If this prevents the calculation to run, use FFTs instead.

ifdtype 
INTEGER 
Default: 
1

Status: 
OPTIONAL

The gradient of the dielectric function is computed in realspace using finite differences.
Different finite differences schemes have been implemented following
P. Holoborodko, Smooth noise robust differentiators, 2008
http://www.holoborodko.com/pavel/numericalmethods/numericalderivative/smoothlownoisedifferentiators
Each scheme can exploit different numbers of points of the realspace grid (as defined by nfdpoint).
ifdtype .EQ. 1 : Central differences
ifdtype .EQ. 2 : Lownoise Lanczos (m=2)
ifdtype .EQ. 3 : Lownoise Lanczos (m=4)
ifdtype .EQ. 4 : Smooth noiserobust (n=2)
ifdtype .EQ. 5 : Smooth noiserobust (n=4)
Central differences are used by default and have been tested more deeply. The other schemes work fine,
but are not deeply tested in terms of performances.

nfdpoint 
INTEGER 
Default: 
1

Status: 
IMPORTANT

Number of point from the realspace grid, to be used by the different finitedifference schemes to compute gradients.
Number of points = 2 * nfdpoint + 1
e.g. ifdtype.EQ.1 .AND. nfdpoint.EQ.1 correspond to central differences with three points
IMPORTANT: nfdpoint .EQ. 1 seems to be enough for most applications, but more refinied finitedifference schemes are
needed (nfdpoint.EQ.2 is enough) for energy conservation in MD simulations in continuum dielectric.
See test case reported in O. Andreussi, I. Dabo and N. Marzari, J. Chem. Phys. 136 064102 (2012)



Namelist: &ELECTROSTATIC

This namelist is not needed if there are no electrostatic embedding effects
problem 
CHARACTER 
Default: 
'poisson'

Status: 
OPTIONAL

Type of electrostatic problem that need to be solved. This keyword is usually set automatically by the
ENVIRON namelist, but it may be used to specify a linearized or modified version of an electrostatic problem.
'poisson' : standard Poisson equation, with or without periodic boundary conditions
'generalized' : generalized Poisson equation, a dielectric embedding must be present
'pb' : nonlinear PoissonBoltzmann equation, an electrolyte embedding must be present,
a dielectric embedding is optional.
'modpb' : nonlinear sizemodified PoissonBoltzmann equation, an electrolyte embedding must
be present, a dielectric embedding is optional.
'linpb' : linearized version of the PoissonBoltzmann problem.
'linmodpb' : linearized version of the modified PoissonBoltzmann problem.

solver 
CHARACTER 
Default: 
'direct'

Status: 
OPTIONAL

Type of numerical solver used to get the solution of the electrostatic problem.
'direct' : Get the direct solution of the problem as provided by the adopted numerical core.
At this time, the FFT numerical core of Environ only allows the 'poisson' problem to be solved directly.
'iterative' : Use a fixedpoint search algorithm (used to be the default for the 'generalized' problem in Environ v0.2).
'sd' : Use a steepestdescent algorithm, possibly preconditioned.
'cg' : Use a conjugategradient algorithm, possibly preconditioned.

auxiliary 
CHARACTER 
Default: 
'none'

Status: 
OPTIONAL

The electrostatic problem is defined and solved in terms of the electrostatic potential or of an auxiliary quantity.
'none' : solve for the electrostatic potential.
'full' : solve for the auxiliary charge (e.g. for 'generalized' problems solve for the polarization charge,
used to be the default in Environ v0.2).

tol 
REAL 
Default: 
1.D5

Status: 
IMPORTANT

Accuracy of the electrostatic calculation: higher accuracies will require more cycles,
but will ensure smoother SCF convergece. As electrostatic solver iterations are usually
cheaper than SCF cycles, it is recommended to increase this accuracy whenever the SCF has problems converging.
The units depend on the actual quantity that is computed by the algorithm, either the potential
(auxiliary = 'none') or an auxiliary charge (auxiliary = 'full'). In the latter case, much smaller thresholds
should be adopted (e.g. lower than 1.D8).

mix 
REAL 
Default: 
0.5

Status: 
OPTIONAL

Linear mixing parameter for iterative solver. Usually does not affect results (and it shouldn't)
and does not affect performances, large values work fine in most common applications.

pbc_dim 
INTEGER 
Default: 
3

Status: 
OPTIONAL

Dimensionality of the simulation cell, i.e. periodic boundary conditions are applied on 3/2/1/0 sides
of the cell.

pbc_axis 
INTEGER 
Default: 
3

Status: 
OPTIONAL

For partially periodic simulation cells (1D or 2D), choice of the sides with periodic boundary conditions.
1 = x, 2 = y, 3 = z, where
if pbc_dim = 2, specified axis is orthogonal to 2D plane.
if pbc_dim = 1, specified axis is along the 1D direction.

pbc_correction 
CHARACTER 
Default: 
'none'

Status: 
OPTIONAL

Type of pbc correction scheme to be used.
'none' : no correction.
'parabolic' : parabolic pointcountercharge (PCC) correction, only implemeted for 0D and 2D systems.



Card: EXTERNAL_CHARGES { bohr  angstrom } 
Syntax:
EXTERNAL_CHARGES { bohr  angstrom
}

Description of items:
Card's options: 
bohr  angstrom

Default: 
(DEPRECATED) bohr

bohr : atomic positions are in cartesian coordinate,
in atomic units (i.e. Bohr radii)
angstrom: atomic positions are in cartesian coordinates,
in Angstrom

Q 
REAL 
total charge of external object

x, y, z

REAL 
positions
NOTE: each atomic coordinate can also be specified
as a simple algebraic expression, see the
description in the input file of PW.

spread 
REAL 
Default: 
0.5

Gaussian spread of the external charge density
in atomic units

dim 
INTEGER 
Default: 
0

dimensionality of the charge density:
dim .EQ. 0 : pointlike (gaussian shaped) charge density
dim .EQ. 1 : linear (gaussian shaped) charge density
dim .EQ. 2 : planar (gaussian shaped) charge density

axis 
INTEGER 
Default: 
3

axis of the external charge density:
if dim.EQ.0 : axis has no meaning/use
if dim.EQ.1 : axis identifies the direction of the linear
charge density: axis.EQ.123 means lines along xyz respectively
if dim.EQ.2 : axis identifies the direction ortogonal to the planar
charge density: axis.EQ.123 means planes ortogonal to xyz



Card: DIELECTRIC_REGIONS { bohr  angstrom } 
Syntax:
DIELECTRIC_REGIONS { bohr  angstrom
}

Description of items:
Card's options: 
bohr  angstrom

Default: 
(DEPRECATED) bohr

bohr : positions are in cartesian coordinate,
in atomic units (i.e. Bohr radii)
angstrom: positions are in cartesian coordinates,
in Angstrom

EpsSt 
REAL 
static permittivity inside of dielectric region

EpsOpt 
REAL 
optical permittivity inside of dielectric region

x, y, z

REAL 
positions
NOTE: each coordinate can also be specified as a simple
algebraic expression, see the description in the
input file of PW.

width 
REAL 
width of the dielectric region in atomic units

spread 
REAL 
Default: 
0.5

spread of the external charge density in atomic units

dim 
INTEGER 
Default: 
0

dimensionality of the dielectric region:
dim .EQ. 0 : spherelike (erfc shaped) region
dim .EQ. 1 : cylinderlike (erfc shaped) region
dim .EQ. 2 : planar (erfc shaped) region

axis 
INTEGER 
Default: 
3

axis of the dielectric region:
if dim.EQ.0 : axis has no meaning/use
if dim.EQ.1 : axis identifies the direction of the linear
charge density: axis.EQ.123 means lines along xyz respectively
if dim.EQ.2 : axis identifies the direction ortogonal to the planar
charge density: axis.EQ.123 means planes ortogonal to xyz



