1 18 BELL SYSTEM TECH NIC A L JOURNA L 



Hexagonal bipyramidal (Class 25) center of symmetry, /? = 



Dihexagonal pyramidal (Class 26) .Y 

 hexagonal Y plane of symmetry 



,0 ,0 ,0 ,/7i5,0 

 ,0 ,0 ,/7i5,0 ,0 



h\ , //31 , /'33 , ,0 ,0 



Dihexagonal bipyramidal (Class 27) center of symmetry, h = 



Cubic tetrahedral-pentagonal-dedo- 

 cahedral (Class 28) A', V, Z binary 



,0 ,0 ,hu,0 ,0 

 ,0 ,0 ,0 , //i4 , 

 ,0 ,0 ,0 ,0 ,/;,4 



Cubic pentagonal-icositetetrahedral (Class 29) ^ = 



Cubic, dyakisdodecahedral (Class 30) center of symmetry, // = 



Cubic, hexakisletrahedral (Class 31) 

 X, I', / quaternary alternating 



,0 ,0 , /;i4 , ,0 

 ,0 ,0 ,0 , //i4 , 

 ,0 ,0 ,0 ,0 ,/7i4 



Cubic, hexakis-octahedral (Class 32) center of symmetry, // = 



This third rank tensor has been expressed in terms of two index symbols 

 rather than the three index tensor symbols, since the two index symbols 

 are commonly used in expressing the piezoelectric effect. The relations 

 for the // and e constants are 



// 14 , /' i5 , // lb are equivalent to // ,23 , // 113 , /' 112 



(136) 



in three index symbols, whereas for the d ij and gij constants we have the 

 relations 



</,4 fl,5 



1 ' T' 



dit 



are equivalent to r/,23 , d,n, ^,12 



(137) 



Hence the </, relations for classes 16, 18, 19, and 22 will be somewhat dif- 

 ferent than the // symbols given above. These classes will be 



