根据书上给出的方程，可以得到如下格波色散关系：

图1  一维双原子晶格的格波色散关系

具体操作如下：

q=-1.8:0.001:1.8;

syms omega1 omega2 beta m1 m2;

a=2;

beta=1;

m1=1;

m2=2;

omega1=sqrt(beta*(m1+m2+sqrt(m1.^2+m2.^2+2*m1.*m2.*cos(q*a)))./(m1*m2));

omega2=sqrt(beta*(m1+m2-sqrt(m1.^2+m2.^2+2*m1.*m2.*cos(q*a)))./(m1*m2));

plot(q,omega1,'-k',q,omega2,'-k','LineWidth',2.0)

line([0,0],[0,2],'Color','k','LineStyle','-','LineWidth',1.0);

line([-pi/2,-pi/2],[0,2],'LineStyle',':','LineWidth',1.0);

line([pi/2,pi/2],[0,2],'LineStyle',':','LineWidth',1.0);

xlabel('\itq','FontName','Times New Roman','FontSize',20);

ylabel('\it\omega','FontName','Times New Roman','FontSize',20);

title('Lattice Dispersion Curve of One-dimensional Diatomic Lattice','FontName','Times New Roman','FontSize',16);

axis([-1.8,1.8,0,2]);

set(0,'defaultfigurecolor','w');