PI EZOELECTKTC CRYSTALS TN TENSOR FORM 



117 



Ditetragonal pyramidal (Class 14) Z 

 quaternary, X and 1' planes of 

 sy mmet ry 



Tetragonal bipyramidal (center of symmtery) h — Q (Class 13) 



, () ,0 ,0 , /;,5 , 

 .0 .0 ,//i5,0 ,0 



/-■■U , /?.l , //33 , ,0 ,0 



Ditetragonal bipyramidal (center of symmetry) // = (Class 15) 



Trigonal pyramidal (Class //u , — //u , , hu , /?i5 , —fi'n 



16) Z trigonal axis / a / / / 



— //22, /^22 , , /;i5 —hu,—fin 



hn , //;u , //3.3 , , , 



Trigonal rhombohedral (Class 17) center of symmetry, // = 



Trigonal trapezohedral (Class 

 18), Z trigonal, .Y binary 



Trigonal bipyramidal (Class 

 19), / trigonal, plane of 

 symmetry 



Ditrigonal pyramidal (Class 

 20) Z trigonal, Y plane of 

 symmetry 



Ditrigonal bipyramidal (Class 

 22) Z trigonal, Z plane of sym- 

 metry and 1' plane of symmetry 



Hexagonal pyramidal (Class 2i) 

 Z hexagonal 



Hexagonal trapezohedral (Class 

 24) Z hexagonal, .Y binary 



