c2x and Castep
Castep was the first electronic structure code supported by c2x, then called check2xsf. Castep-specific support currently includes:
- reading and writing .cell files
- reading and writing .den_fmt files
- reading .check, .castep_bin, .chdiff, .orbitals and .cst_esp files
1. a .castep_bin is essentially a .check file without the wavefunctions;
2. .cst_esp and .chdiff files contain just a grid of data with no information about the axes of that grid. So they need to be read in conjunction with a .cell or .check file.
Note that c2x can regenerate a .den_fmt file, including scalar spin density, from a .check file.
Many different formats of the .cell file can be written. One has a choice between Angstroms and Bohr, between absolute and relative atomic positions, and between Cartesian axes or a, b, c, α, β, γ. Not all data in .cell files are preserved by c2x: it is assumed that its output is taken as a starting-point for generating a new input file, and not simply blindly accepted.