Warning: Failure at t=6.137539e-04. Unable to meet integration tolerances without reducing the step size below the smallest value allowed (1.734723e-18) at time t. In ode15s (line 730) In khademi (line 59)
All of the MATLAB ode solvers adjust the integration step size to try to keep the error in the solution less than certain prescribed tolerances. If the error exceeds these tolerances, the step size is reduced until it reaches essentially zero (1.734723e-18).
Usually this error message arises because the problem is ill-posed. If you terminate the solution at some value of t<6.137539e-04 and look at the solution at that time, there is a good chance it will be very large (i.e. the solution is going to infinity or negative infinity).