c2x and Siesta
Siesta is a GPLed linear-scaling DFT code using localised basis states.
From version 2.14a, c2x can read much of the syntax of Siesta's
.fdf (flexible data format) input files. In most cases it can read
the cell, atom positions, and initial colinear spins. It supports
.fdf's include file syntax, both
%includefile and <,
regarding paths as relative to the current directory, not the
directory of the file being processed.
When specifying initial colinear spins, + is interpreted as +1, not maximum possible spin, and similarly -.
From version 2.31 c2x can also read Siesta's .XV and .RHO files, and version 2.32 adds .VH and .VT files, which are rescaled to volts. When reading .RHO files, an attempt is made to find and read .psf files to obtain ionic charges so that total charge, dipole moments and electrostatic potential can be calculated.
c2x has always been able to write .fdf files. Support for colinear spins was added in 2.14a.
RHO files containing charge density can be written in all versions, and from 2.31 spin density can also be written. .XV files can also be written from version 2.31 onwards, although velocities are written as zero.