// Monte Carlo simulation with the // Metropolis scheme for spinodal decomposition import java.lang.*; import java.util.*; import java.io.*; import java.awt.*; // uses the abstract windowing toolkit public class Exchang { // change the following globals to suit your fancy: static int maxSize = 200; // width of window in pixels static int dim = 100; // lattice size; can be any divisor of maxSize static int squareWidth = maxSize / dim; static Graphics g; // the frame's graphics object, for drawing into static int frameTop, frameLeft; // platform-dependent width of frame's top and left edges static Color upColor = new Color(00,160,60); static Color downColor = new Color(255,245,220); static int seed; static int ic; //counter for the current iteration static final int nsize = 10000; static final int nskip = 10000; static final int pskip = 100; //replot lattice after pskip iterations static final int ntotal = nsize*nskip; //total number of iterations static final int neq = 0; //# of iterations for equilibriation static final int lx = dim; //dimensions of lattice static final int ly = dim; //dimensions of lattice static int iaccept = 0; // counter for calculating the acceptance rate of attempted jumps static int at; static double r1, r2; static double fn = 0.5; //fraction of negative spin sites static double fp = 1 - fn; //fraction of positive spin sites static int a[][] = new int[lx][ly]; // array that stores the spins in the lattice static int nb[][] = new int[lx][ly]; //# of B atoms on lattice sites nearest to site (i,j) static Random r = new Random(); static int rmax = dim/2 + 1; // maximum correlation length static double Teq = 1.0; //for equilibriation at temperature Teq before final simulations static double T1 = 1.5; //temperature at which simulation is to be done static double T; static double jaa = 30; static double jbb = 30; static double jab = 28; public static void main(String argv[]) { // initialize window and graphics: Frame gWin = new Frame("Exchang Model"); gWin.setLocation(50,50); // screen coordinates of top left corner gWin.setResizable(false); gWin.setVisible(true); // show it! Insets theInsets = gWin.getInsets(); gWin.setSize(maxSize+theInsets.left+theInsets.right,maxSize+theInsets.top+theInsets.bottom); frameTop = theInsets.top; frameLeft = theInsets.left; long resumeTime = System.currentTimeMillis() + 1000; do {} while (System.currentTimeMillis() < resumeTime); // wait for frame to get initialized g = gWin.getGraphics(); // stick graphics object into a global so we can draw from anywhere! FileOutputStream out; PrintStream p; // Initiate the seed from the current time GregorianCalendar t = new GregorianCalendar(); int t1 = t.get(Calendar.SECOND); int t2 = t.get(Calendar.MINUTE); int t3 = t.get(Calendar.HOUR_OF_DAY); int t4 = t.get(Calendar.DAY_OF_MONTH); int t5 = t.get(Calendar.MONTH) + 1; int t6 = t.get(Calendar.YEAR); seed = t6+70*(t5+12*(t4+31*(t3+23*(t2+59*t1)))); if((seed%2) == 0) seed = seed-1; initial(a); //initializes spins System.out.println("\n" + "Initial spins: "); //create new files for writing output try{ out = new FileOutputStream("corExchang.dat",false); p = new PrintStream(out); p.print("\n"); p.close(); } catch(Exception e){ System.err.println("Error in printing to file"); } double accept = 0; //Equilibriate at temperature T; //System.out.println(accept + " " + i); for(int i=0; i negative spin else a[i][j] = 1; // 1 --> positive spin } at = 0; for(int i=0; i