(*An example of the electronic correlation and anticorrelation in some wave functions for 
the hydrogen molecule. First, the Heitler-London, and then the Hartree-Fock
 wave functions are analyzed. In both cases electron 1 is located on nucleus  a (left) 
and we look at the values of the wave function calculated at different positions of electron  
 2. It is seen, that in the case of the Heitler-London function electron 2 runs in panic to nucleus  b, 
while in case of the Hartree-Fock function nothing like that happens: electron  2 does not distinguish between 
the two nuclei*)
R=4.
pi=3.141592532 
a=(Sqrt[(1/pi)]) (E^(-(Sqrt[(x^2)+(y^2)])))
b=(Sqrt[(1/pi)]) (E^(-(Sqrt[(((x-R))^2)+(y^2)])))
S=(1+R+((R^2)/3)) (E^(-R))
Heitler=(((Sqrt[(1/pi)]) (b+(E^(-R)) a))/(Sqrt[2 (1+(S^2))]))
Plot3D[Heitler,{x,-2.,6.},{y,-2.,2.},PlotPoints->24]
HFock=(((Sqrt[(1/pi)]) (a+b+(E^(-R)) a+(E^(-R)) b))/((Sqrt[1+(S^2)]) 2))
Plot3D[HFock,{x,-2.,6.},{y,-2.,2.},PlotPoints->25]