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

Optimized Structure

 3.482716   -0.879297   -1.322832
 0.000136    0.143594   -1.306042
 0.001240   -3.184513    0.082738
 1.954111   -0.426156    1.969243
 2.069200    2.827332   -0.034448
-1.955140   -0.428053    1.969079
-2.069805    2.826229   -0.034088
-3.482458   -0.879136   -1.323650

                    Distance matrix (angstroms):
                    1          2          3          4          5
     1  Ca   0.000000
     2  Ca   3.629732   0.000000
     3  Ca   4.405714   3.606246   0.000000
     4  Ca   3.657831   3.856180   3.870548   0.000000
     5  Ca   4.170979   3.619451   6.358653   3.822722   0.000000
     6  Ca   6.372643   3.856981   3.870888   3.909251   5.550402
     7  Ca   6.798697   3.619261   6.358608   5.548265   4.139005
     8  Ca   6.965174   3.629703   4.407816   6.372175   6.798591
                    6          7          8
     6  Ca   0.000000
     7  Ca   3.823111   0.000000
     8  Ca   3.657627   4.169926   0.000000



SCF Done:  E(RB+HF-PW91) =  -5420.25506981 au

 E(8 atoms of Calcium) = -5420.078262 au

 Binding Energy = 4.8112 ev (0.6014 ev/atom)