The nano-materialsLa(0.8)Ca(0.1)Pb(0.1)Fe(1-x)CO(x)O(3) (x = 0.00 to 0.20) were prepared by the sol-gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray dispersion (EDS). The structure refinement of the XRD data was performed using the Rietveld method. These compounds were found to exhibit a single phase and crystallize in the orthorhombic structure with Prima space group. The chemical analysis by EDS shows the successful incorporation of Co (Cobalt) in the parent sample. The volume was found to decrease with the increase of the cobalt-content. The volume decrease was also investigated theoretically by comparing the total energies of LaFeO3 and LaCoO3 compounds which were calculated within density functional theory (DFT). We find an almost agreement between experimental and theoretical results, provided we use the correct SGGA + U functional (in contrast to the SGGA Spin polarized Generalized Gradient Approximation), which takes properly into account the strong electron correlation in the open d-shell by a Hubbard-like U term. Our analysis of the corresponding densities of states indicates a qualitatively different ground state behavior of the Fe- or Co-ion.