Inorganic structures in space groupP31m; coordinate analysis and systematic prediction of new ferroelectrics

Abstract

The 62 entries listed in ICSD release 2009/1 under polar space group P31m correspond to 31 families of inorganic crystal structures, some with only one member. Coordinate analysis reveals, over a wide confidence range, 11 of these families as ferroelectric candidates. One includes the well known improper ferroelectric GASH (guanidinium aluminum sulfate hexahydrate), [(C(NH(2))(3))Al(SO(4))(2)(H(2)O)(6)], another the previously predicted ferroelectric CsNO(3) phase II. Those remaining include K(3)Nb(3)B(2)O(12), the minerals schairerite, galeite and lizardite 1T, LaNi(5)D(6) and gamma-CaNi(5)D(6.1), Ca(OCl)(2)Ca(OH)(2), [N(CH(3))(4)](2)Mo(3)S(13), Li(17)Ag(3)Sn(6) and Cs(3)As(5)O(9). Candidate selection is based upon detecting an approach by the reported atomic arrangement to the symmetry of a corresponding nonpolar supergroup. A further 13 families are typified by their reduced predictive properties, with four others likely to remain polar at higher temperatures and the remaining three noted as having a unit cell larger than reported or a misassigned space group. The primary sources of uncertainty in structurally based predictions of ferroelectricity are the reliability of the underlying structural determination and the upper limit assigned to the cationic displacement magnitudes required to achieve supergroup symmetry.

Systematization of Simple and Binary Silicates According to Relationship “Composition– Structure–Property”

“…Previously, several models were tested for systematization and taxonomy of known binary and ternary crystals to see empirical relations helpful in creation of new complex NCS materials with valuable properties [7,[22][23][24][25][26][27][28][29]. In the present study a systematization of NCS silicates will be developed, and crystal chemical relations promising for creation complex NLO silicates will be considered.…”