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

Optimized Structure

 4.965755   -0.025495   -0.000972
 2.099849   -2.747572    0.004570
 1.617681    0.463095   -1.904951
 1.619747    0.470952    1.904659
 0.661746    3.625484   -0.006406
-1.242387   -2.157741    1.908676
-1.243913   -2.167091   -1.905287
-4.366528   -0.790880    0.002193
-2.056438    1.660382   -1.921007
-2.055511    1.668867    1.918524

                    Distance matrix (angstroms):
                    1          2          3          4          5
     1  Ca   0.000000
     2  Ca   3.952613   0.000000
     3  Ca   3.882455   3.766581   0.000000
     4  Ca   3.882481   3.768253   3.809618   0.000000
     5  Ca   5.643950   6.533307   3.810380   3.810644   0.000000
     6  Ca   6.836245   3.891537   5.439900   3.886110   6.382708
     7  Ca   6.839066   3.894260   3.886721   5.447523   6.386801
     8  Ca   9.363617   6.755936   6.404717   6.406799   6.692376
     9  Ca   7.472610   6.357092   3.864311   5.437352   3.862104
    10  Ca   7.473520   6.358866   5.437388   3.865581   3.862279
                    6          7          8          9         10
     6  Ca   0.000000
     7  Ca   3.813975   0.000000
     8  Ca   3.906820   3.909368   0.000000
     9  Ca   5.468749   3.912799   3.878647   0.000000
    10  Ca   3.912058   5.476751   3.881170   3.839541   0.000000

SCF Done:  E(RB+HF-PW91) =  -6775.34004638 au

E(10 atoms of Calcium) = -6775.0978286 au

Binding Energy = 6.5911 ev (0.65911 ev/atom)