Clear[u1, u2, c1, 
      c2, T, Vnn, Vne, Vee]
c0 = {k1 ->  1.0,  k2 ->  1.0, s1 ->  0.27885572, 
          s2 ->  0.0, Z ->  3.0};
c1 = {k1 ->  1.0289716,  k2 ->  1.23924503, 
          s1 ->  0.27885572, s2 ->  0.07, 
          Z ->  3.0};
  
c2 = {k1 ->  1.03,  k2 ->  1.0, s1 ->  0.27885572, 
          s2 ->  0.00, 
          Z ->  3.0};

Vne = -2*3*Z/Q - 4*Z/(P + Q) - 
          2*Z/(P + Q);
Vee = 
        2*4/(P + Q) + 4/(P + Q) + 3*s2/P + 
          2*3*s1/Q;
Vnn = Z*Z/(P + Q)/2;
T = 2.25*k2/P^2 + 2*2.25*k1/Q^2;
func = T + Vne + Vee + Vnn  /.  c0
N[t = FindMinimum[func,  {P, 2.0}, {Q, 0.6}], 10]

u0 = t[[1]];
u1 = t[[2]];
N[-(Vne + Vee + Vnn)/T  /. u1  /. c0, 
      10]
N[(u0 + 2*(Z - s1)^2/k1)*27.2114  /.  c0,  
      10]
N[2*(P + Q)*0.529177  /. u1  /. c0, 10]

func = 
      T + Vne + Vee + Vnn  /.  c2
N[t = FindMinimum[func,  {P, 2.5}, {Q, 0.6}], 
      10]
u3 = t[[1]];
u2 = t[[2]];
N[-(Vne + Vee + Vnn)/T  /. u2  /. c2, 
      10]
N[(u3 + 2*(Z - s1)^2/k1)*27.2114  /.  c2,  
      10]
N[2*(P + Q)*0.529177  /. u2 /. c2, 10]