New ferroelectric inorganic materials predicted in point group 4mm

The Inorganic Crystal Structure Database contains a total of 209 entries for 128 different materials reported in point group 4mm, of which eight are for previously known ferroelectrics. Analysis of the remaining entries, assuming the structure determinations reported are correct, leads to the prediction of an additional 43 new ferroelectric materials. 15 were determined in space group P4mm, 11 in P4bm, one in P4(2)nm, one in P4cc, two in P4(2)mc, one in P4(2)bc, seven in I4mm, two in I4cm, one in I4(1)md and two in I4(1)cd. Numerous other structures are shown to have been assigned, most likely, to an incorrect space group. All but one of the materials reported in space group P4bm are predicted to be ferroelectric. New ferroelectrics predicted in point group 4mm include K-2[Pt(CN)(4)]Br-0.3.H2O, Nd0.33TaO3, YBaCuFeO5+delta, Ba-2(TiO)(Si2O7), K-2(NbO)(2)(SiO3)(4), Ba6CoNb9O30, Sr2SbMnO6, Hg2AlF5.(H2O), Rb5Nb3OF18 and SrNi2(VO4)(2).