Sample JAVA program to calculate two-electron atoms (ions).

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If you copy and paste the program source code below into a text editor, you can easily compile and run this.
(This class file name is twoele, so save this text editor as "", and compile it.)
In this program, we first input atomic number Z = 2, 3, 4, 5, 6, 7, 8, 9, or 10.
Next we input the initial x-coordinate r1 (in MM) of electron 1, and the absolute value of the total energy E (in eV) of two-electron atoms (ions).
From the inputted values, this program outputs the y component of electron 1 velocity after a quarter of its orbit, and WN (the number of de Broglie's waves included in one quarter of the orbital).
Here 1 SS = 1 × 10-23 second and 1 MM = 1 × 10-14 meter.
The initial x-coodinate is automatically increased per calculation until +100.

import java.util.Scanner;
 class twoele {
 public static void main(String[] args) {
                                  // input Z, r1 and |E|
 Scanner stdIn=new Scanner(;
 System.out.println("Atomic number Z ? (He=2, Li+=3, Be2+=4, B3+=5, C4+=6, N5+=7...)");  
 double Z=stdIn.nextDouble();
 System.out.println("r1 between nucleus and electron 1 (MM)? ");  
 double r=stdIn.nextDouble();
 System.out.println("total energy |E| of the two-electron atom (eV) ? ");  
 double E=stdIn.nextDouble();
 double me=9.1093826e-31;
 double pai=3.141592653589793; double epsi=8.85418781787346e-12;
 double h=6.62606896e-34; double ele=1.60217653e-19; double nucle=2.0*me; double nuclee=0.0;
 if (Z == 2 ) { nucle = 6.64465650e-27; nuclee=nucle;}   // He alpha particle
 if (Z == 3 ) { nucle = 1.1646e-26; nuclee=nucle;}   // Li7 nucleus
 double rm=(2.0*me*nucle)/(2.0*me+nuclee); rm=rm*0.5;    // reduced mass ( He, Li )

 double Ene=-((4.0*Z-1)*(4.0*Z-1)*ele*ele*ele*ele*me)/(64.0*epsi*epsi*h*h);
 Ene=Ene*6.241509e18; System.out.printf("Wrong Ene:%.3f\n", Ene);  // Energy of circular orbit

 for (int i=1;i < 100;i++) {      // repeat until r1=initial r1+100
                             // poten = potential energy 
double poten=-(2.0*Z*ele*ele)/(4.0*pai*epsi*r)+(ele*ele)/(4.0*pai*epsi*2.0*r);
                             //vya= total E-potential energy  
double vya=-(E*1.60217646e-19)-poten*1.0e14; 
 if (vya > 0) {
                               // vyb=electron initial velocity (m/sec) 
 double vyb=Math.sqrt(vya/me); 
 double VY=vyb*1.0e-9;         // change m/sec to MM/SS
 double prexx=r; double VX=0.0; double WN=0.0; double preyy=0.0; 
 double yy,vk,preVY,preWN,midWN,leng,wav; double xx=0.0;
 do {
    xx=prexx+VX; yy=preyy+VY;        //electron 1 position after 1SS
    preVY=VY;preWN=WN ;
    leng=Math.sqrt(vk)*1.0e-14;      // moving length (m) for 1 SS
     wav=h/(rm*Math.sqrt(vk)*1.0e9);  // de Broglie wavelength (m) 
    WN=WN+leng/wav;                  // add de Broglie wavelength      
                                   //calculation of VX,VY from Coulomb force
    double ra=Math.sqrt(prexx*prexx+preyy*preyy);  // between nucleus and electron     
    double rb=Math.sqrt(4.0*prexx*prexx+2.0*preyy*preyy); // between two electrons
                                   // change MM to meter
    ra=ra*1.0e-14; rb=rb*1.0e-14; 
    prexx=prexx*1.0e-14; preyy=preyy*1.0e-14;
    double ac=(ele*ele)/(4.0*pai*epsi*rm);
                                    // acceleration (MM/SS^2)
   } while (xx >=0);              // electron has moved one quater of an orbit? 
   if (VY > -0.0001 && VY < 0.0001) {    // last VY condition           
  System.out.print("r1: "+r+"   ");
  System.out.printf("VX:%.6f", VX);
  System.out.printf("VY:%.6f", VY);
  System.out.printf("preVY:%.6f", preVY);
  midWN=(preWN+WN)/2.0; System.out.printf("midWN:%.6f\n", midWN);
   }  r=r+1;