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

Optimized Structure

-4.668447    1.585908    0.263269
 0.010900   -2.403026   -1.335283
-0.990563   -3.223588    2.422687
 1.434902    1.113667   -1.451563
-1.340324    3.586796   -0.258856
-2.179349    0.519339   -2.469359
 4.850071    1.224189    0.207489
-1.200912    0.244692    1.235317
 1.721021    2.551981    2.080740
 2.279340   -1.238875    1.507519
-3.721505   -2.184013   -0.243931
 3.804866   -1.777073   -1.958026


                    Distance matrix (angstroms):
                    1          2          3          4          5
     1  Ca   0.000000
     2  Ca   6.353208   0.000000
     3  Ca   6.428154   3.974744   0.000000
     4  Ca   6.357242   3.795844   6.301149   0.000000
     5  Ca   3.918235   6.233977   7.327642   3.903946   0.000000
     6  Ca   3.847133   3.824073   6.273343   3.801571   3.872929
     7  Ca   9.525552   6.241347   7.668301   3.798428   6.642318
     8  Ca   3.842855   3.884184   3.671929   3.862895   3.663557
     9  Ca   6.712808   6.256662   6.389587   3.824628   3.989535
    10  Ca   7.602585   3.818715   3.933051   3.873461   6.285630
    11  Ca   3.919981   3.894851   3.955959   6.238718   6.242794
    12  Ca   9.383006   3.895356   6.654261   3.772215   7.624385
                    6          7          8          9         10
     6  Ca   0.000000
     7  Ca   7.554805   0.000000
     8  Ca   3.841535   6.215323   0.000000
     9  Ca   6.328343   3.881115   3.817855   0.000000
    10  Ca   6.227903   3.790175   3.793049   3.874389   0.000000
    11  Ca   3.826079   9.235342   3.800023   7.579896   6.322262
    12  Ca   6.430069   3.845709   6.272382   6.276523   3.824511
                   11         12
    11  Ca   0.000000
    12  Ca   7.729811   0.000000

    
SCF Done:  E(RB+HF-PW91) =  -8130.45077967 au

E(12 atoms of Calcium) = -8130.117394 au

Binding Energy = 9.07195 ev (0.7560 ev/atom)