THE QUANTUM PHYSICS OF SOLIDS 



671 



h- >■ 



uj q: T 



(a) 



LlXiXUJ 



(h) 



WAVE FUNCTIONS 



NORMAL MODES 



(b) 



-rOl 



_Q— 1=^— a — a-. 



(L) 



XT"-°--^ 



(j) -^ 



izr-v 



-o- 



--izr 



y ^ 



(I) 



-izr 



.□x 



-d_n- 



,0. 



(m) 



^ 





xlZk 





(n) 



X2( 



V^ 



J 



(o) 

 Fig. 11 — A one-dimensional crystal and some mechanical and electrical analogues. 



(a) The potential energy of an electron for points on 



a line through the nuclei. 



(b) to (g) Wave functions for points on the same line, 

 (h) Coupled oscillators. 



(i) to (n) Their normal modes of vibration, 

 (o) Coupled circuits. 



