Using Gaussian98
#b3pw91/6-311g(d) scf=direct fopt

Optimized Geometry

 0.000000    2.856244   -0.528209
-2.856244    0.000000   -0.528209
 0.000000   -2.856244   -0.528209
 2.856244    0.000000   -0.528209
 0.000000    0.000000    2.112835

                    Distance matrix (angstroms):
                    1          2          3          4          5
     1  Ca   0.000000
     2  Ca   4.039338   0.000000
     3  Ca   5.712487   4.039338   0.000000
     4  Ca   4.039338   5.712487   4.039338   0.000000
     5  Ca   3.890146   3.890146   3.890146   3.890146   0.000000


 SCF Done:  E(RB+HF-PW91) =  -3387.61127326 au

 E(5 atoms of Calcium) = -3387.548914 au

 Binding Energy = 1.6969 ev (0.3394 ev/atom)