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

Optimized Structure

 0.000000    3.126804    1.209773
 0.000000    0.000000   -0.107832
 0.000000    0.000000    3.505554
-2.005121   -2.005121   -2.059203
 3.126804    0.000000    1.209773
-3.126804    0.000000    1.209773
 0.000000   -3.126804    1.209773
 2.005121    2.005121   -2.059203
 2.005121   -2.005121   -2.059203
-2.005121    2.005121   -2.059203


                    Distance matrix (angstroms):
                    1          2          3          4          5
     1  Ca   0.000000
     2  Ca   3.393079   0.000000
     3  Ca   3.879112   3.613386   0.000000
     4  Ca   6.406509   3.442219   6.245602   0.000000
     5  Ca   4.421968   3.393079   3.879112   6.406509   0.000000
     6  Ca   4.421968   3.393079   3.879112   3.995608   6.253607
     7  Ca   6.253607   3.393079   3.879112   3.995608   4.421968
     8  Ca   3.995608   3.442219   6.245602   5.671338   3.995608
     9  Ca   6.406509   3.442219   6.245602   4.010242   3.995608
    10  Ca   3.995608   3.442219   6.245602   4.010242   6.406509
                    6          7          8          9         10
     6  Ca   0.000000
     7  Ca   4.421968   0.000000
     8  Ca   6.406509   6.406509   0.000000
     9  Ca   6.406509   3.995608   4.010242   0.000000
    10  Ca   3.995608   6.406509   4.010242   5.671338   0.000000

SCF Done:  E(RB+HF-PW91) =  -6775.37407132 au

E(10 atoms of Calcium) = -6775.0978286 au

Binding Energy = 7.5170 ev (0.7517 ev/atom)