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 -r8 -fast -o ising ising.f90

Note that I had to use double precision (-r8) 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