A DFT study of homonuclear X-2 (X = Ge, As, Se, Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Zn) is presented using PBEO exchange (xc) functional which is a mixing of Perdew-Burke-Ernzerhof (PBE) and Hartree Fock (HF) exchange energy. However, we used cc-pVXZ and aug-cc-pVXZ basis sets where X is maximum angular momentum number in basis set. Convergence pattern of binding energy with respect to basis set was observed. Two-point extrapolations to complete basis set (CBS) limit were applied to speed up convergence and decrease the basis set incompleteness error (BSIE). Counterpoise correction (CP) method was utilized to alleviate basis set superposition errors (BSSE). Both CP-corrected and uncorrected binding energies were obtained and compared with the experimental and theoretical binding energy values in literature.