Data type: char
'Ca ((Cl O3)2 O)2 (H2 O)6'
'(Pt (N H3)2 (C5 H7 N3 O)2) (Cl O4)2'
See _chemical_formula_ for the rules for writing chemical formulae for inorganics, organometallics, metal complexes etc., in which bonded groups are preserved as discrete entities within parentheses, with post-multipliers as required. The order of the elements should give as much information as possible about the chemical structure. Parentheses may be used and nested as required. This formula should correspond to the structure as actually reported, i.e. trace elements not included in atom type and atom site lists should not be included in this formula (see also _chemical_formula_analytical).