Environ Input

pw.x: input description

Input File Description

Program: pw.x / Environ / Quantum Espresso

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
         non-electrostatic contributions modelled via pressure ( env_pressure = -0.35 GPa )
         and surface tension ( env_surface_tension = 50 dyn/cm ) effects (see references below).
         For electrons-dependent interfaces (self-consistent 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 ions-dependent interfaces (soft-sphere 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).

'water-cation':
         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).

'water-anion':
         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 real-space grid in the form of
                  *.cube files
verbose .GE. 3  dumping of several intermediate physical quantites on the real-space 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 good-enough 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.d-1
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 system-dependent properties in Environ (e.g. see later system-dependent 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 surface-dependent 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
quantum-surface 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
non-electrostatic 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 volume-dependet 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 non-electrostatic 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 counter-charge 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 Stern-layer 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 Poisson-Boltzmann 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 point-like 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 self-consist. on electronic density, corresponds
       to the Self-consistent Continuum Solvation approach (SCCS).

'ionic':
       interface defined on atomic positions, corresponds to the
       Soft-sphere 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 density-dependent interface function,
roughly corresponding to the density threshold of the continuum model.
         
rhomin REAL
Default: 0.0001
Status: OPTIONAL
Second parameter of the density-dependent interface function, when stype=1.
         
tbeta REAL
Default: 4.8
Status: OPTIONAL
Second parameter of the density-dependent interface function, when stype=0.
         
alpha REAL
Default: 1.0
Status: OPTIONAL
Main parameter of ions-dependent 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 soft-sphere functions used for the ions-dependent interfaces.
         
solvent_distance REAL
Default: 1.0
Status: OPTIONAL
Distance of the system-dependent 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 system-dependent 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 self-consist. on electronic density, corresponds
       to the Self-consistent Continuum Solvation approach (SCCS).

'ionic':
       interface defined on atomic positions, corresponds to the
       Soft-sphere 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 density-dependent 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 density-dependent interface function, when stype=1.
Used for the electrolyte interface.
         
stern_tbeta REAL
Default: 4.8
Status: OPTIONAL
Second parameter of the density-dependent interface function, when stype=0
Used for the electrolyte interface.
         
stern_alpha REAL
Default: 1.0
Status: OPTIONAL
Main parameter of ions-dependent 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 soft-sphere functions used for the ions-dependent interfaces.
Used for the electrolyte interface.
         
stern_distance REAL
Default: 1.0
Status: OPTIONAL
Distance of the system-dependent 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 system-dependent 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 non-electrostatic 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 ions-dependent 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.10024-10035 (1992)
         
solvationrad(i), i=1,ntyp REAL
Default: 3.0
Status: OPTIONAL
Atomic radii used for the ions-dependent 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 atomic-centered 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 solvent-aware 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 solvent-aware 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 non-locality of the algorithm.
         
radial_spread REAL
Default: 0.5
Status: OPTIONAL
For solvent-aware interfaces, numerical spread of the step function used to compute the filled fraction.
         
filling_threshold REAL
Default: 0.825
Status: OPTIONAL
For solvent-aware interfaces, threshold of filled-fraction 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 solvent-aware 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 real-space coordinates or QM degrees of freedom.

'fft'      : fast Fourier transform
'fd'       : finite differences in real-space
'analytic' : analytic derivatives for as much as possible (and FFTs for the rest)

NOTE: analytic derivatives, especially for ions-dependent 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 real-space using finite differences.
Different finite differences schemes have been implemented following
P. Holoborodko, Smooth noise robust differentiators, 2008
http://www.holoborodko.com/pavel/numerical-methods/numerical-derivative/smooth-low-noise-differentiators
Each scheme can exploit different numbers of points of the real-space grid (as defined by nfdpoint).

ifdtype .EQ. 1 : Central differences
ifdtype .EQ. 2 : Low-noise Lanczos (m=2)
ifdtype .EQ. 3 : Low-noise Lanczos (m=4)
ifdtype .EQ. 4 : Smooth noise-robust (n=2)
ifdtype .EQ. 5 : Smooth noise-robust (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 real-space grid, to be used by the different finite-difference 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 finite-difference 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'          : non-linear Poisson-Boltzmann equation, an electrolyte embedding must be present,
                a dielectric embedding is optional.
'modpb'       : non-linear size-modified Poisson-Boltzmann equation, an electrolyte embedding must
                be present, a dielectric embedding is optional.
'linpb'       : linearized version of the Poisson-Boltzmann problem.
'linmodpb'    : linearized version of the modified Poisson-Boltzmann 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 fixed-point search algorithm (used to be the default for the 'generalized' problem in Environ v0.2).
'sd'        : Use a steepest-descent algorithm, possibly preconditioned.
'cg'        : Use a conjugate-gradient 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.D-5
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.D-8).
         
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 point-counter-charge (PCC) correction, only implemeted for 0D and 2D systems.
         

Card: EXTERNAL_CHARGES { bohr | angstrom }

Syntax:

EXTERNAL_CHARGES { bohr | angstrom }
 Q(1)   x(1)   y(1)   z(1)  {  spread(1)   dim(1)   axis(1)  }
 Q(2)   x(2)   y(2)   z(2)  {  spread(2)   dim(2)   axis(2)  }
 . . .
 Q(nec)   x(nec)   y(nec)   z(nec)  {  spread(nec)   dim(nec)   axis(nec)  }

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 : point-like (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.1|2|3 means lines along x|y|z respectively

if dim.EQ.2 : axis identifies the direction ortogonal to the planar
charge density: axis.EQ.1|2|3 means planes ortogonal to x|y|z
                     

Card: DIELECTRIC_REGIONS { bohr | angstrom }

Syntax:

DIELECTRIC_REGIONS { bohr | angstrom }
 EpsSt(1)   EpsOpt(1)   x(1)   y(1)   z(1)   width(1)  {  spread(1)   dim(1)   axis(1)  }
 EpsSt(2)   EpsOpt(2)   x(2)   y(2)   z(2)   width(2)  {  spread(2)   dim(2)   axis(2)  }
 . . .
 EpsSt(ndr)   EpsOpt(ndr)   x(ndr)   y(ndr)   z(ndr)   width(ndr)  {  spread(ndr)   dim(ndr)   axis(ndr)  }

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 : sphere-like (erfc shaped) region

dim .EQ. 1 : cylinder-like (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.1|2|3 means lines along x|y|z respectively

if dim.EQ.2 : axis identifies the direction ortogonal to the planar
charge density: axis.EQ.1|2|3 means planes ortogonal to x|y|z
                     
This file has been created by helpdoc utility.