This program works as a Monte Carlo spin crossover simulation in
Ising model aproximation. It generates output file with 3 columns - 
temperature, energy and magnetization. Programs like gnuplot can be 
used to make graphs. 

***Building
Use build script compile.sh to compile with Intel Fortran Compiler, 
or gfortran_compile.sh to compile with GNU Fortran: 
"chmod +x compile.sh && ./compile.sh"

***Running
First set your input according to the input structure below in file in.2d. 
Then simply run compiled file: 
"./a.out"

*****INPUT STRUCTURE is 4 LINES
1        30         1         0.00     ! Lattice, L, J, delta, r
100     150      100                   ! T_initial, T_final, TSTEPS
300      1089561                       ! ntimes, iseed for RNG
2				       ! q; q=1 one-way, q=2 up-down


LINE 1 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
LINE 1: MC code works for LATTICE=
  1= square
  2= triangular
  3= rhombohedral

LINE 1: Box Size L=
  5 = repeated 5   sites per direction
  10= repeated 10  sites per direction

LINE 1: J=  magnetitude and sign  of nearest neighbor interaction
  V = -1   FM Ising Model
  V = +1  AFM Ising Model

LINE 1: delta= chemical potential difference
 mu = 0  no external field (or 50% up and 50% dn)

LINE 1: r= effective degeneracy ratio
 r = 2000
LINE 1 +++++++++++++++++++++++++++++++++++++++++++++++++++++++

LINE 2 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
LINE 2:  T_initial = starting temperature (CANNOT BE ZERO !!!!)
  T_initial = 1  temperature in units of delta 

LINE 2:  T_final   = final    temperature (CANNOT BE ZERO !!!!)
  T_final = 200   temperature in units of delta

LINE 2:  TSTEPS = steps in temperature
  TSTEPS = 10  (MUST BE INTEGER)
LINE 2 +++++++++++++++++++++++++++++++++++++++++++++++++++++++


LINE 3 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
LINE 3:  ntimes = Integer  Number of sample for avg. 
   ntimes= 125       (e.g.)

LINE 3:   iseed = directly change RNG seed to do multiple runs.
    iseed= 1089561   (e.g.)
LINE 3 +++++++++++++++++++++++++++++++++++++++++++++++++++++++

LINE 4 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
LINE 4:  q = boolean integer to set the nature of simulation
   q= 1 one-way MC SCO simulation
   q= 2 temperature goes up and then down (or vice versa)
LINE 4 +++++++++++++++++++++++++++++++++++++++++++++++++++++++

*****OUTPUT STRUCTURE

output
   T, E/atom, Mag/atom

*** M. Blasko et al., 2022 ***