Domain

The Domain block of the parameter file for pscf_pc or pscf_pg contains information about the periodic unit cell and discretization mesh for a D-dimensional periodic structure. Here D is the dimension of space specified by the argument of the "-d" command line option used to invoked pscf_pc or pscf_pg.

An example of a Domain block used for an SCFT calculation for a three dimensional (D=3) gyroid structure is shown below:

Domain{
  mesh         32  32  32
  lattice      cubic
  groupName    Ia-3d
}

The parameter file format is:

Domain{
  mesh         IntVec<D>
  lattice      string
  groupName*   string
}

Here, the data type IntVec<D> denotes a D-dimensional vector represented in the parameter file by a list of D positive integers. The meaning of each parameter is described below:

mesh	A list of D integers on a single line, in which component i is the number of mesh points along direction (Bravais basis vector) i of a a regular computational mesh.
lattice	String identifier for a lattice system (e.g., cubic, orthorhombic, hexagonal, etc.). The lattice system is stored internally as a UnitCell<D>::LatticeSype enum value. A discussion of allowed crystal system identifiers and associated unit cell parameters is given here.
groupName*	String identifier for a crystallographic space group (optional). A list of valid space group identifiers for each value of D is given here.

The mesh and lattice parameter are needed for both SCFT and PS-FTS calculations, and are required.

The optional groupName parameter may only be used for SCFT, but not for stochastic FTS calculations. This optional parameter must be present to enable reading and writing of fields in symmetry adapted basis format, and to enable use of any algorithm that relies on that symmetry-adapted field representation. Specifically, the groupName parameter must be present to enable iterative solution of SCFT equations for structures of known symmetry using an iterator algorithm that uses a symmetry-adapted basis to update the fields, such as the AmIteratorBasis algorithm.

The groupName parameter should, however, be omitted from parameter files used to initialize field theoretic BD or MC simulations. The fields generated during the course of such a stochastic simulation generally do not exactly preserve any nontrivial symmetry. The groupName parameter may also be omitted for "large-cell" SCFT calculations performed with pscf_pg in which no symmetry is imposed. Fields for PS-FTS calculations or large SCFT calculations that do not impose a space group symmetry are normally input and output using the r-grid field file format.

Because the AmIteratorBasis algorithm is currently the only iterator algorithm provided for use with pscf_pc, the groupName parameter actually must be included in any parameter file that is used to perform SCFT calculations with this program. The groupName parameter may be omitted from a parameter file used to perfom an SCFT calculation with pscf_pg, however, if the calculation is performed using the AmIteratorGrid algorithm, which does not impose any space group symmetry. the AmIteratorGrid