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

Optimized Structure

 4.570964    0.000044   -0.000258
-4.569515   -0.000108   -0.000052
 1.637997   -2.708799   -0.004984
 1.637819    2.708830    0.005097
 1.638033   -0.005064    2.708322
 1.637821    0.005158   -2.708359
-1.638120   -1.918318    1.912343
-1.638277    1.912340    1.918411
-1.638303   -1.912407   -1.918271
-1.638418    1.918323   -1.912250

                    Distance matrix (angstroms):
                    1          2          3          4          5
     1  Ca   0.000000
     2  Ca   9.140479   0.000000
     3  Ca   3.992512   6.772757   0.000000
     4  Ca   3.992604   6.772693   5.417638   0.000000
     5  Ca   3.992307   6.772663   3.830432   3.830489   0.000000
     6  Ca   3.992138   6.772442   3.830640   3.830494   5.416691
     7  Ca   6.774281   3.991223   3.877363   5.981627   3.876506
     8  Ca   6.774425   3.991255   5.982336   3.876593   3.877448
     9  Ca   6.774308   3.991046   3.876732   5.982320   5.981446
    10  Ca   6.774358   3.991016   5.981874   3.877480   5.981993
                    6          7          8          9         10
     6  Ca   0.000000
     7  Ca   5.981842   0.000000
     8  Ca   5.981401   3.830663   0.000000
     9  Ca   3.877407   3.830619   5.417455   0.000000
    10  Ca   3.876562   5.417317   3.830666   3.830735   0.000000

SCF Done:  E(RB+HF-PW91) =  -6775.33306917 au

E(10 atoms of Calcium) = -6775.0978286 au

Binding Energy = 6.40127 ev (0.640127 ev/atom)