Finite Differences-Semi discretization method on Heat Equation

Hi!, I'm working on a personal project: Solve the heat equation with the semi discretization method, using my own Mathematica's code, (W. Mathematica 9). The code:

Attachment 71725



I'm having problems with the variable M (the number of steps). It works with M=1-5, but no further, I do not know what's going on. Help!!!!

Also, I'm looking for a better animation more intuitive.

Thanks a lot

Attached Files

PDE heat.nb (12.5 KB)