In terms of density functional theory calculations, we explored the reason why the neutron diffraction patterns of a crystalline solid, NaFe2(H3O2)-(MoO4)(2), are explained by invoking the simultaneous presence of two widely different magnetic structures. The partitioning into OH and H2O groups of the "H3O2" units, which interconnect Feat chains in each [Fe-2(H3O2)-(MoO4)(2)](-) layer, leads to various layers different only in their H-atom positions. The crystal structure containing only symmetric FeO2(HO)(H2O) chains and that containing only asymmetric FeO4 chains are found to be responsible for the two observed magnetic structures.