The ground state (X(1) Sigma(g)(+)) of beryllium dimer was investigate
d within the frozen-core approximation at the full CI level with the b
asis set containing bond functions (BFs). The role of the BFs in the c
alculations was examined in detail. In each case, the BSSE was also ev
aluated according to Boys and Bernardi. The improved results for the X
(1) Sigma(g)(+) of beryllium driller show that the BFs method is a goo
d alternative approach in the calculation of the molecules containing
shallow potential well.