(* Ar atom Kimball, Ne-center, outer-sp-spheres 21.12.2011 *)
Clear[k1,k2,k3,sig1,sig2,sig3,c,z,R1,R2,R3];
c = {k1 -> 1.0, k2 -> 1.0, k3 -> 1.0, sig1 -> 0.4, sig2 -> 0.4, sig3 -> 0.4};

T = 2.25*k1/R1^2+4.5*2.0*k2/R^2 /. c;
ad = 8./3.; 
Vee=3.0*sig1/R1+4.0*3.0*sig2/R2+16/(R1+R2)+24/((R1+R2)*Sqrt[ad]) /. c;
Vne=-3.0*z/R1-8*z/(R1+R2);
S2 = R2*4^(1/3);
T = T + 9/R3^2;
Vee = Vee+12*sig3/R3+80/(S2+R3)+24/((S2+R3)*Sqrt[ad]) /. c;
Vne = Vne-8*z/(S2+R3);

func = T + Vee + Vne;

t = Table[FindMinimum[func, {R1,0.1}, {R2,0.4}, {R3,1.0}], {z,18,26}]

Table[N[Vne /. c /. t[[{z-17},2]],10], {z,18,26}]
Table[N[Vee /. c /. t[[{z-17},2]],10], {z,18,26}]
Table[N[-(Vee+Vne)/T /. c /. t[[{z-17},2]],10], {z,18,26}]
Table[N[(S2+R3) /. c /. t[[{z-17},2]],10], {z,18,26}]