The structural and electronic properties of La$_{2-x}$Ba$_x$CuO$_4$ were investigated as a function of Ba-concentration $0 \leq x \leq 1.2$, within the virtual crystal approximation (VCA) by means of first-principles total-energy calculations. We found Ba doping induces a quasi-rigid displacement of Cu d$_{x^{2}-y^{2}}$ and d$_{z^{2}}$ bands toward higher energies. This effect generates important changes in the Fermi surface topology, which manage to imitate the ARPES momentum distribution map (MDM) measurements and tight-binding calculations recently reported for doped La-based cuprates. The calculations exhibit the significant increase in the contribution of Cu d$_{z^{2}}$ states at the Fermi level for greater Ba doping content to 0.3, which has effects on orbital hybridisation with Cu d$_{x^{2}-y^{2}}$ states and therefore in the suppression of the superconducting state. For this Ba doping range, no magnetism was found. Comment: 5 figures
