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

Optimized Structure

-2.034768    1.174774    2.459414
 0.000000    0.000000    0.000000
 0.000000    3.513016    0.000000
 3.042361   -1.756508    0.000000
-2.034768    1.174774   -2.459414
 2.034768    1.174774    2.459414
 2.034768    1.174774   -2.459414
-3.042361   -1.756508    0.000000
 0.000000   -2.349548   -2.459414
 0.000000   -2.349548    2.459414

                    Distance matrix (angstroms):
                    1          2          3          4          5
     1  Ca   0.000000
     2  Ca   3.401337   0.000000
     3  Ca   3.956814   3.513016   0.000000
     4  Ca   6.357544   3.513016   6.084722   0.000000
     5  Ca   4.918828   3.401337   3.956814   6.357544   0.000000
     6  Ca   4.069536   3.401337   3.956814   3.956814   6.384042
     7  Ca   6.384042   3.401337   3.956814   3.956814   4.069536
     8  Ca   3.956814   3.513016   6.084722   6.084722   3.956814
     9  Ca   6.384042   3.401337   6.357544   3.956814   4.069536
    10  Ca   4.069536   3.401337   6.357544   3.956814   6.384042
                    6          7          8          9         10
     6  Ca   0.000000
     7  Ca   4.918828   0.000000
     8  Ca   6.357544   6.357544   0.000000
     9  Ca   6.384042   4.069536   3.956814   0.000000
    10  Ca   4.069536   6.384042   3.956814   4.918828   0.000000

SCF Done:  E(RB+HF-PW91) =  -6775.37392400 au

E(10 atoms of Calcium) = -6775.0978286 au

Binding Energy = 7.5136 ev (0.7514 ev/atom)