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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 field file
a command 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. This file defines the basic parameters of a physical problem of interest, and is used to initialize the state of the program. The parameter file contains basic physical information about chemical structures (e.g., monomer properties and block polymer structures), the composition of the system of interest, interactions among the constituents (Flory-Huggins chi parameters), a description of the spatial domain of interest (e.g., a unit cell of a periodic structure), a description of a spatial discretization of that domain, and some other algorithmic parameters. The name of the parameter file is specified as command line argument when a PSCF program is invoked, as the argument of the "-p" command line option.

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 solver

An example of a simple parameter file for the pscf_fd program is presented and discussed 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. Every SCFT calculation must read an input file that contains an initial guess for the self-consistent field chemical potential fields. The name of the required input field file is given as a parameter to a command in the command file.

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 within the file. The name of the command file is also specified by a command line argument (the argument of the "-c" command line option).

Many commands in a command file require field data to be read from or written to specific data files. For example, the first step in solving a SCFT problem is usually to read an initial guess for the chemical potential fields from an input field file. The last steps of such a computation may then include writing 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.

Each line of a command file starts with a capitalized command name, followed by zero or more arguments. A simple command file for using one of the pscf_pc programs to perform an SCFT calculation might look like this:

READ_W_BASIS      in/w.bf
ITERATE
WRITE_W_BASIS     out/w.bf
WRITE_C_RGRID     out/c.rf
FINISH

This file instructs the program to:

READ_W_BASIS: Read in a chemical potential (w) field in symmetrized Fourier basis from a file named in/w.bf
ITERATE: Iteratively solve the SCFT equation, using the iterator initialized in the parameter file.
WRITE_W_BASIS: Write the converged chemical potential fields (w-fields) in symmetrized Fourier basis format to a file out/w.bf
WRITE_C_RGRID: Write the corresponding monomer concentration fields (c-fields) in real-space grid (r-grid) format to a file out/c.rf
FINISH: finish execution and halt the main program

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