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Hello everyone,

I have a problem for making POSCAR for free energy calculation. A compound ABC4 crystalized cubic structure with fm-3m symmetry (z=4). The atom position is A:4a; B:4b; C:32f (1/2 occupancy).
Who can tell me how should I do if I want to calculate total energy?

If in a crystal only half of the sites of a sublattice are occupied, you have to construct a larger supercell, containing at least one occupied C site and one vacancy (site not occupied) in sublattice C. Please be aware that this sublattice is periodically repeated, i.e. it corresponds to an ordered structure.