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

Optimized Geometry

 0.000000    2.122658    0.000000
 1.838276   -1.061329    0.000000
 0.000000    0.000000    3.264936
-1.838276   -1.061329    0.000000
 0.000000    0.000000   -3.264936

                    Distance matrix (angstroms):
                    1          2          3          4          5
     1  Ca   0.000000
     2  Ca   3.676552   0.000000
     3  Ca   3.894288   3.894288   0.000000
     4  Ca   3.676552   3.676552   3.894288   0.000000
     5  Ca   3.894288   3.894288   6.529871   3.894288   0.000000

 SCF Done:  E(RB+HF-PW91) =  -3387.63692780 au

 E(5 atoms of Calcium) = -3387.548914 au

 Binding Energy = 2.3951 ev (0.4790 ev/atom)