function plot_SolidStateCh3Problem5

i = sqrt(-1.0);
pi = 4.0*atan(1.0);
N1=0.0;
N2=pi;
dn = .1;
K=(N1:dn:N2);
radical_term = 11.0-0.25*(20.0-10.0*exp(i*K)-10.0*exp(-i*K));
radical = sqrt(radical_term);
w1 = sqrt(11+radical);
w2 = sqrt(11-radical);
gcf = figure('Color',[1 1 1])
hold off;
cla; % clear the screen
hold on;
plot(K,real(w1),'color',[0 .7 0],'LineWidth',2);
plot(K,real(w2),'LineWidth',2);
plot([pi pi],[2.5 4],'--k');
title('Dispersion Curve','fontsize',20);
xlabel('K [1/a]','fontsize',16);
ylabel('Phonon Frequency \omega [C/M]','fontsize',16);
