Use of the Inorganic Crystal Structure Database as a problem solving tool

The information in the Inorganic Crystal Structure Database (ICSD) can be used to determine the structures of new compounds by analogy; this database is thus a useful tool for practical problem solving. A model for the structure of (NH(4))Fe(CO(3))(OH)(2) [Cmcm, a = 6.6154 (6), b = 12.0639 (10), c = 6.0263 (5) A, Z = 4] was found by searching the ICSD for compounds with C-centered orthorhombic cells and containing C, H, N and O. [Al(H(2)O)(6)](2)[Al(H(2)O)(5)(SO(4))](2)-(H(3)O)(2)(SO(4))(5) [P1;, a = 12.5881 (5), b = 13.0726 (5), c = 7.3354 (2) A, alpha = 108.162 (2), beta = 70.536 (2), gamma = 112.658 (2) degrees, Z = 1] is isostructural to a Cr compound of the same stoichiometry, which was located by searching on the formula type ANX = A4B7X52. Suitable models for MgCl(2)(H(2)O)(4) [P2(1)/c, a = 5.9001 (9), b = 7.2709 (7), c = 8.4199 (7) A, beta = 111.007 (15) degrees, Z = 2], MgCl(2)(H(2)O)(2) [C2/m, a = 7.3886 (29), b = 8.5498 (24), c = 3.6488 (17) A, beta = 98.96 (3) degrees, Z = 2], and MgCl(2)(H(2)O) [Pnma, a = 8.899 (7), b = 3.6339 (20), c = 11.398 (8) A, Z = 4] were located by combining searches on chemistry and formula type. Quantum-chemical calculations were performed on all five structures to locate the H-atom positions and to obtain quantitative understanding of the hydrogen bonding important in all the structures.