318 



BELL SYSTEM TECHNICAL JOURNAL 



That is, 

 iV(the vector normal to the atomic plane hk-t) 







V3 



h + 2k 







/ -\A/t > 

 = \A/i \/h 



\ -\/h / 







- V3 

 /; + 2y^ 

 1.1// 



f 1.1V3 1 



\A/M 

 V3 



The unit vector N = 



h 

 h + 2k 



VI. 1 





(3.13) 



(3.14) 



where S is the sum of the squares of the three terms of N. For example, 

 for the (01-1) plane (^ = 0, ^ = i, t = 1), we find from equation (3.13) 

 that 



N = f 2/ V3 

 \ 1/1.1/ 



(3.15) 



whence 5 — 4/3 + 



1.21 



2.159 (3.16) 



and the unit vector normal N — I .7857 I (3.17) 



\.6186/ 



which means that A^ is perpendicular to the X axis, makes an angle with 

 Y whose cosine is .7857 ( = 38° 13') and an angle with Z whose cosine is 

 .6186 ( = 51° 47'). 



