We present the results of ab initio hybrid density-functional calculations of the atomic and the electronic structures of ${\text{LaMnO}}_3$ (LMO) and ${\text{La}}_{1-x_b}{\text{Sr}}_{x_b}{\text{MnO}}_3$ (001) surfaces. The total energies obtained from these calculations were used to analyze thermodynamic stability of the surfaces. We predict Sr and O vacancy segregation to the surface to occur with similar energies ($\sim 0.5\text{eV}$ per defect). In pure LMO only ${\text{MnO}}_2$ termination is thermodynamically favorable under typical operational conditions of a cathode in solid oxide fuel cells, whereas Sr doping makes La(Sr)O termination favorable. Finally, the role of Sr doping in cathode degradation is discussed.

• Received 13 August 2008

DOI:https://doi.org/10.1103/PhysRevB.78.121406