438 



BELL SYSTEM TECHNICAL JOURNAL 



For a left-handed crystal a positive angle is in a counter-clockwise 

 direction. 



In the section dealing with elastic and piezo-electric constants for 

 rotated crystals (page 449) is given a method for determining the elastic 

 constants of a rotated crystal and curves are given for the ten elastic 

 constants. These have been worked out by Mr. R. A. Sykes of the 

 Laboratories. The method of designation is the following: The X 

 axis remains fixed and is designated by 1'. The axis of greatest length 

 is designated by 2' , since in the unrotated crystal the mechanical axis, 

 corresponding to the F direction, is the axis of greatest length. Exten- 

 sional motion perpendicular to the 2' axis is designanted by 3', and 

 shear motion in the plane determined by the 2', 3' axes is designated by 

 4'. The ten resulting constants ^n', 522', 533', 544', 512', ^13', Sm' s^', 

 s<ii , Szi are shown evaluated in terms of the angle d on Fig. 30. Since 



5 10 



-90 -80 -70 -60 -50 -40 -30 -20 -10 10 20 30 40 50 60 70 80 90 

 ANGLE OF ROTATION IN DEGREES 



Fig. 30 — Elastic compliances of a perpendicularly cut crystal as a function of the 



angle of rotation. 



motion and coupling to motion along the X axis can be neglected, the 

 constants of interest are 522', S33', Sa', 523', ^24', ^34'. Since the 2' or 3;' 



