This dialog is used when exporting data either for SIESTA, the DFT program for calculating forces by molecular-orbital methods, or its auxiliary program VIBRATOR which can use force output from VIBRATZ as well as SIESTA to calculate crystal vibrational dispersion relationships (not just kappa=0 or gamma-point vibrations).
The export of data when setting up a SIESTA calculation is covered in the section on importing SIESTA files. Briefly, this export option writes a .fdf file which contains the unit cell and atom locations, but usually the SIESTA calculation parameters will have to be edited in that file.
The remainder of this section describes the output for VIBRATOR, for complete dispersion calculations on crystals.
The VIBRATOR auxiliary program in the SIESTA package can calculate frequencies for all phonons, not just optical vibrations at kappa=0 (the gamma point), but it does not do symmetry. VIBRATZ can can set up supercells and calculate a Cartesian force-constant matrix for input into VIBRATOR. This is done with the Export files for VIBRATOR option in the Forces menu. The output will be a .fdf file for input into VIBRATOR as well as a .FC (Cartesian forces) file with the same name. VIBRATOR inputs a .fdf with most of the same parameters as required for SIESTA, but with some additions. You must specify in the Export files for VIBRATOR dialog the number of unit cells to be added in each crystal or polymer axis direction. Adding one unit cell in all three directions will give 27 total unit cells; adding two will give 125 total cells, etc. The file name by default is myfile_vibra.fdf. The .fdf file will have an arbitrary or sample "%block BandLines" section which specifies the points or lines in reciprocal- or k-space to be calculated. These will likely not be appropriate for your particular problem and will have to be modified - this can be done with a word-processor. Other modifications to the .fdf file may be necessary.
VIBRATZ can also export a .fdf file with supercell specifications for calculation by SIESTA of the forces (.FC file) for later use in VIBRATOR. For this you must specify the Export data for SIESTA option and give the number of extra unit cells in each axis direction. The resulting .fdf file will work in SIESTA, but will need to be modified for use in VIBRATOR.