ode45 gets stuck when making the function a column vector?

I am trying to solve a relatively simple ode. I am aware I could possibly use a different ode function but don't think that is the problem.

I get the very common error that my function must return a column vector, so then add the dx=zeros(2,1) line into my function.

When I do this however the programme doesn't complete - it starts but then seems to get stuck somehow, busy.

If I instead transpose my dx to get a column vector, the result is the same.

This is my function:

function dx = minibandvel(t,x)

F=1^(-20);
tau=10^(-5);%s
del=19.1*10^(-3);%eV
d=8.241*10^(-9);%m
hbar=10.5*10^(-34);

%dx=zeros(2,1);
dx(1)=((tau*del)/(2*hbar))*sin(x(2));
dx(2)=(F*d*tau)/hbar;

%dx=dx.';
end

used in this:

close all
clc
initialx(1)=0;
initialx(2)=0;
tspan=[0 0.1];

[t,x]= ode45 (@minibandvel,tspan,[initialx(1) initialx(2)]);
plot (t,x)

The odd thing is that I had run the programme several times successfully; and had this issue before but it could be solved by simply restarting MATLAB.

Thanks in advance

Answer 1

[Star Strider]

Looking at your constants:

tau=10^(-5);%s
del=19.1*10^(-3);%eV
d=8.241*10^(-9);%m
hbar=10.5*10^(-34);

The ode45 solver will get there, but it could take several hours. A better — and certainly faster — solution is a ‘stiff’ solver such as ode15s.

[Physics]

Thanks for your reply.

The solution I found was to define the fraction used and then input that into the ODEs.

For example, fraction=(F*d*tau)/hbar;

and then

dx(2)=fraction

[Star Strider]

My pleasure!