ATOM
This keyword introduces the information about one atom in the unit cell.
Two labels are needed for the atoms. The second one should be the name of the element. This is not used internally but it is convenient for compatibility with other programs reading the same file. The two labels are followed by three fractional coordinates. The program generates the rest of atoms in the unit cell.
ATOM Cu Cu 0.2341 0.5000 0.00000
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