Above about , Rochelle salt (potassium sodium tartrate tetrahydrate, KNaC H O H O)…
PHYSICS · Multi-part · Fermi University Physics · Mathematical Methods for Physics · Condensed Matter, Materials & Soft Matter · Crystal structure, bonding and diffraction
Solid State Physics, Ch Symmetry and the classification of crystals
Problem
Above about 24∘C, Rochelle salt (potassium sodium tartrate tetrahydrate, KNaC4H4O6⋅4H2O) has point group 222: the identity and three mutually perpendicular two-fold rotations, one along each of the orthorhombic axes a, b and c, with no mirror plane and no inversion centre.
((a)) Using the rule that all noncentrosymmetric point groups except 432 are piezoelectric, decide whether Rochelle salt, in this phase, can be piezoelectric.
((b)) Decide whether Rochelle salt crystals of this phase can be grown in two distinguishable (left- and right-handed) forms, and whether they can be optically active.
((c)) The ten polar point groups are 1,2,m,mm2,3,3m,4,4mm,6,6mm. Decide whether Rochelle salt, in this phase, can be pyroelectric.