Systematic prediction of new ferroelectrics in space groups P31 and P32

Release 2002/2 of the Inorganic Crystal Structure Database (FIZ Karlsruhe, Germany, and Institute Laue-Langevin, Grenoble, France) contains 62 entries in space group P3(1) and ten entries in space group P3(2) for 49 different materials including eight families with two or more isostructural members. The structural criteria for ferroelectricity are satisfied for 16 new structure types at a confidence level that depends on the reliability of each determination. LaBGeO5, a mineral with stillwellite structure, was previously reported as ferroelectric and forms an additional family with seven other members or related structures that satisfy the criteria. Ten structures reported in space group P3(1) or P3(2) are dubious or incorrect, with atomic coordinates that satisfy supergroup symmetry. One material is probably pyroelectric but is unlikely to become ferroelectric, and three others are either incompletely solved or incompletely refined. Among the predicted new ferroelectrics are Cu2BaGeS4, Fe-3(Fe,Si)O-4(OH)(5), Se4S5, K2HCr2AsO10, IV-RbNO3, Rb2Sc(NO3)(5), Na3ReO5, Nd-14(GeO4)(2)(BO3)(6)O-8, CsHgCl3, Ba2Cu2AlF11, KYF4, SrS2O6.4H(2)O, Cu3PbTeO6(OH)(2), ReH(CO)(4), Ni-2(NH3)(9)Mo(CN)(8).2H(2)O and the 6T polytype of Ca1.89Ta1.80Sm0.16Ti0.10O7, in addition to beta-LaBSiO5, PbBAsO5 and BaBAsO5 in the stillwellite family.