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Types of File

To perform a typical self-consistent field theory (SCFT) calculation, a PSCF program generally reads three different types of input file:

a parameter file
a command file
a field file

All PSCF programs use similar formats for the parameter and command files. Several different formats are used for field files.

Parameter file

When any PSCF program is executed, the parameter file is processed first. The name of the parameter file is specified as command line argument when a PSCF program is invoked, as a parameter of the required "-p" command line option.

The parameter file defines the basic parameters of a physical problem of interest, and is used to initialize the state of the program. This file contains physical information about chemical structures (e.g., monomer properties and block polymer chemical structures), the composition of the system of interest (the volume fraction or chemical potential of each species in a mixture), interactions among the constituents (Flory-Huggins chi parameters), information about the spatial domain of interest (e.g., the Bravai lattice type of a periodic structure), a description of a spatial discretization of that domain, and a variety of algorithmic parameters.

The information that must be provided in a parameter file depends somewhat on what type of calculation are going to be performed, as dictated by the commands in the associated command file. The parameter file for a simple SCFT calculation generally contains the following 4 sections:

Mixture: Description of the structure of all molecular species and composition of a mixture
Interaction: Flory-Huggins interaction parameters
Domain: Description of a spatial domain or unit cell, and a spatial discretization.
Iterator: Algorithmic parameters used by an iterative SCFT solver

An example of a simple parameter file for the pscf_1d program is shown here .

Command file

The command file is processed after the parameter file, and controls program flow after initialization. The command file is a script that contains a list of commands that are interpreted and executed in the order they appear. Each line of a command file starts with a capitalized command name, followed by zero or more arguments. The name of the command file that controls a calculation is always specified as a required command line argument, as the parameter of the "-c" command line option.

Some commands in a command file perform operations that perform file input and output operations on field data. For example, the first command in a command file for a simple SCFT calculation is usually a command to read an initial guess for the monomer chemical potential fields from an input field file. The last commands in such a script are often commands that write the converged chemical potential and monomer concentration fields to output files. The names of these input and output field files and various other data files are specified as parameters of commands within the command file.

An example of a simple command file for a 1D SCFT calculation performed with the pscf_1d program is shown here .

Field file

A field file contains a description of a set of fields (i.e., functions of position) that are associated with different monomer types. Several different field formats are used by different programs in the PSCF package. For each program, the same file format or file formats are used to describe both monomer chemical potential fields and monomer volume fraction fields. The command file for every SCFT and FTS calculation generally includes a command that reads an input file containing an initial set of chemical potential fields.

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