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

Optimized Structure

-2.105801   -1.517145    1.629493
-3.182519    2.063269    0.367901
 1.690788   -1.595793    2.908388
-1.962761   -0.488926   -2.190570
 0.161248    2.277951    2.643339
 4.007313   -1.712695   -0.200097
 0.134936    3.109888   -1.438105
 0.630434    0.070568    0.093844
 0.485313   -3.258528   -0.759849
 3.522110    2.083722    0.271423
 2.006142   -0.023940   -3.057896
-5.387203   -1.008370   -0.267870

                    Distance matrix (angstroms):
                    1          2          3          4          5
     1  Ca   0.000000
     2  Ca   3.945922   0.000000
     3  Ca   4.006975   6.602418   0.000000
     4  Ca   3.958608   3.814090   6.369690   0.000000
     5  Ca   4.535433   4.050245   4.173205   5.961015   0.000000
     6  Ca   6.384027   8.140897   3.878483   6.411036   6.229173
     7  Ca   5.986693   3.919512   6.592125   4.232966   4.165453
     8  Ca   3.516537   4.310983   3.438425   3.500891   3.404791
     9  Ca   3.931316   6.560971   4.204024   3.963676   6.506866
    10  Ca   6.817916   6.705354   4.883253   6.539399   4.118143
    11  Ca   6.411658   6.558562   6.177922   4.089090   6.419222
    12  Ca   3.824453   3.834032   7.780208   3.961490   7.075334
                    6          7          8          9         10
     6  Ca   0.000000
     7  Ca   6.307557   0.000000
     8  Ca   3.830110   3.439455   0.000000
     9  Ca   3.886825   6.414009   3.439874   0.000000
    10  Ca   3.856233   3.930452   3.527905   6.230995   0.000000
    11  Ca   3.876028   3.993246   3.440199   4.249294   4.221938
    12  Ca   9.421125   6.987383   6.124288   6.308066   9.446043
                   11         12
    11  Ca   0.000000
    12  Ca   7.963347   0.000000


SCF Done:  E(RB+HF-PW91) =  -8130.44713860 au

E(12 atoms of Calcium) = -8130.117394 au

Binding Energy = 8.972878 ev (0.7477 ev/atom)