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

Optimized Structure

 0.000000    2.270636    0.000000
 1.966429   -1.135318    0.000000
-1.966429   -1.135318    0.000000


                 Distance matrix (angstroms):
                    1          2          3
     1  Ca   0.000000
     2  Ca   3.932991   0.000000
     3  Ca   3.933709   3.933709   0.000000


 SCF Done:  E(RB+HF-PW91) =  -2032.55364841

 E(3 atoms of Calcium) = -2032.529348

 Binding Energy = 0.6612 ev (0.2204 ev/atom)

Single Point Energy Calculation
b3pw91/6-311+g(df)
34.5 minutes
-2032.55387827
B.E. = 0.221704696