(* Na atom nach Kimball, Aussen-sp-Kugeln 10.12.2011/11.06.2012 *)
Clear[k0,k2,sig0,sig2,c,z,R1,R2,R3,a];
c = {k1 -> 1.0, k2 -> 1.0, k3->1.0,sig1 -> 0.3, sig2 -> 0.3, sig3->0.3};

T = 2.25*k1/R1^2+9.0*k2/R2^2+1.125*k3/R3^2 /. c;
ad = 8./3.;  a = (R1+R2)/3+Sqrt[(R2+R3)^2-8*(R1+R2)^2/9];
Vee=3.0*sig1/R1+4.0*3.0*sig2/R2+16/(R1+R2)+24/((R1+R2)*Sqrt[ad])+2/a+6/(R2+R3)+2/(R1+R2+a) /. c;
Vne=-3.0*z/R1-8*z/(R1+R2)-z/a;

func = T + Vee + Vne;

t = Table[N[FindMinimum[func, {R1,0.13}, {R2,0.4}, {R3,2.0},{MaxIterations -> 500}], 20], {z,11,26}]

Table[N[Vne /. c /. t[[{z-10},2]],10], {z,11,26}]
Table[N[Vee /. c /. t[[{z-10},2]],10], {z,11,26}]
Table[N[-(Vee+Vne)/T /. c /. t[[{z-10},2]],10], {z,11,26}]
Table[N[a /. c /. t[[{z-10},2]],10], {z,11,26}]