1D双原子格子 M MC M2 C MiC M, Us-1 Vs-1 Us Us+1 Vs+1 F=FR+FL M =C(v,-u-u.+V.)=C(v.+V.-2u.) dt2 M, d'vs dt2 =C(u+1-V。-V+u)=C(u1+u-2vs》 组试探解 u,(t)=uexpli(kx,-@t)] V,(①)=vexp[ikx。-ot)] 这里X=sa黄春晖 编 1D 双原子格子 M2 M1 C C M2 M1 C M2 C C M1 M2 M1 us-1 vs-1 us vs us+1 vs+1 C(u v v u ) C(u u 2v ) dt d v M C(v u u v ) C(v v 2u ) dt d u M F F F 2 s 1 s s s s 1 s s s 2 2 2 s s s s 1 s s 1 s s 2 1 s R L = − − + = + − = − − + = + − = + + + − − a 一组试探解 这里 xs=sa [ ( )] v (t) v exp[ ] ( ) kx t u (t) u exp kx t s s s s ω ω = − = − i i