/* From: "A SURVEY OF COMPUTATIONAL PHYSICS" 
   by RH Landau, MJ Paez, and CC BORDEIANU 
   Copyright Princeton University Press, Princeton, 2008.
   Electronic Materials copyright: R Landau, Oregon State Univ, 2008;
   MJ Paez, Univ Antioquia, 2008; and CC BORDEIANU, Univ Bucharest, 2008.
   Support by National Science Foundation                              
   */
//  Harmos.java: t-dependent Schro eqn, for wavepacket in harmonic oscillator V
import java.io.*;

public class Harmos  {

  public static void main(String[] argv) throws IOException, FileNotFoundException  {
    PrintWriter w =  new PrintWriter(new FileOutputStream("Harmos.dat"), true);
    double psr[][] = new double[751][2], psi[][] = new double[751][2]; 
    double p2[] = new double[751], v[] = new double[751], dx=0.02, k0, dt, x, pi;
    int i, n, max = 750;
    pi   = 3.14159265358979323846;	k0 = 3.0*pi;	dt = dx*dx/4.0;   x = -7.5;// i.c.
    for( i=0; i < max; i++)  {       
      psr[i][0] = Math.exp(-0.5*(Math.pow((x/0.5), 2.))) * Math.cos(k0*x);  // RePsi
      psi[i][0] = Math.exp(-0.5*(Math.pow((x/0.5), 2.))) * Math.sin(k0*x);  // ImPsi
      v[i] = 5.0*x*x;                                                   // Potential
      x    = x + dx;
    }
    for ( n=0; n < 20000; n++)  {                               // Propagate in time
      for( i=1; i < max-1; i++ )  {                                         // RePsi
        psr[i][1] = psr[i][0] - dt*(psi[i+1][0] + psi[i-1][0]    
                   -2.*psi[i][0])/(dx*dx)+dt*v[i]*psi[i][0];
        p2[i] = psr[i][0]*psr[i][1]+psi[i][0]*psi[i][0];             
      }
      for ( i=1; i < max-1; i++ )  { psi[i][1] = psi[i][0] + dt*(psr[i+1][1] 
				   + psr[i-1][1] -2.*psr[i][1])/(dx*dx)-dt*v[i]*psr[i][1]; }        // ImPsi
      if ( (n == 0) || (n%2000 == 0) ) {                  // Output every 2000 steps
        for( i=0; i<max; i=i+10 ) w.println(""+(p2[i]+0.0015*v[i])+"");
        w.println("");   
      }     
      for ( i=0; i<max; i++ )   {psi[i][0] = psi[i][1]; psr[i][0] = psr[i][1];} 
    }
    System.out.println("data saved in Harmos.dat");
} }