﻿ Two electron atom program

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

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 MathMethod, so save this text editor as "MathMethod.java", and compile it.)
In this program, first we input the initial x-coordinate r1 (in MM) of electron 1, and the absolute value of the total energy E (in eV) of helium atom.
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 MathMethod {
public static void main(String[] args) {

// input  r1 and |E|
Scanner stdIn=new Scanner(System.in);
System.out.println("r1 between nucleus and electron 1 (MM)？ ");
double r=stdIn.nextDouble();
System.out.println("total energy |E| of helium 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 Z = 2.0;    // Helium atomic number
double nucle = 6.64465650e-27;  // He alpha particle

double rm=(2.0*me*nucle)/(2.0*me+nucle); rm=rm*0.5;    // reduced mass

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 ;
vk=VX*VX+VY*VY;
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)
VX=VX+1.0e-32*ac*prexx*(-Z/(ra*ra*ra)+2.0/(rb*rb*rb));
VY=VY+1.0e-32*ac*preyy*(-Z/(ra*ra*ra)+1.0/(rb*rb*rb));
prexx=xx;preyy=yy;

} 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;
}}}

``````