Ab initio study on the effect of A-site doping on the stability, equilibrium volume, activation energy barrier, and oxygen diffusivity in La2-xAxNiO4+δ

This study employs ab initio calculations to systematically evaluate the stability, equilibrium volumes, activation energy barriers, and oxygen diffusion properties of La 2-x A x NiO 4+δ (A = Ca, Sr, Ba; x = 0, 0.125, 0.25). The findings indicate that Ca and Sr doping leads to a reduction in the equilibrium volume, while Ba induces a slight increase. Additionally, doping with any of these three elements increases the formation energy, thereby reducing the overall stability of the material. The activation energy barrier is primarily dictated by ionic size, with smaller ions such as Ca lowering the barrier, while larger ions, including Sr and Ba, increase it. The dominant oxygen diffusion pathway varies with dopant type, with Path #1 (Intersticialcy mechanism along the ab plane) being the preferred mechanism in Sr- and Ba-doped compounds. Ca doping improves both the oxygen diffusion coefficient and ionic conductivity, whereas Sr and Ba result in reduced values for these properties. These results provide valuable insights for the optimization of oxygen transport in La 2-x A x NiO 4+δ . • The stability and activation energy barrier of La 2-x A x NiO 4+δ with different A-site dopants were predicted. • The partition function was used to estimate the average energy barrier across diffusion paths. • Ca doping enhances oxygen diffusivity in La 2-x A x NiO 4+δ . • La 2-x Ca x NiO 4+δ shows the highest attempt frequency among the studied compounds.