This directory includes codes to simulate the 2D Ising model [1,2].  We will 
use these codes to visualize the system near criticality, perform finite size
scaling and Monte Carlo RG calculations.

This code was adapted from http://fraden.brandeis.edu/courses/phys39/simulations/Student%20Ising%20Swarthmore.pdf
I had to fix several bugs. I was able to compile it with 

ifort -fast -o ising ising.f90

If your compiler is old, be sure to use 64 bit precision to prevent overflows 
and underflows.

You may use xmgrace to plot the various quantities.  I.e. to see the specific 
heat versus T, use

xmgrace -block energy -bxy 1:4

the energy

xmgrace -block energy -bxy 1:2

the susceptibility

xmgrace -block magnetization  -bxy 1:4

the magnetization

xmgrace -block magnetization  -bxy 1:2

For the finite size scaling calculations, the following compound command may
prove useful

./Ising; mv energy energy_16; mv magnetization magnetization_16

To visualize the spins you must install idl or gdl (gnudl), and then run 

gdl
.run see_spins.idl

(Chinedu figured out how to do this).


Some useful references
1. Jacques Kotze, Introduction to Monte Carlo methods for an Ising Model 
of a Ferromagnet, http://arxiv.org/pdf/0803.0217.pdf
2. Somendra M. Bhattacharjee and Avinash Khare, Fifty Years of the Exact 
solution of the Two-dimensional Ising Model by Onsager, 
http://homepages.warwick.ac.uk/~masdbn/9511003.pdf
3. Lilian Witthauer and Manuel Dieterle
http://quantumtheory.physik.unibas.ch/people/bruder/Semesterprojekte2007/p1/index.html