Structure and Electronic Properties of Cerium Orthophosphate: Theory and Experiment

Structure and Electronic Properties of Cerium Orthophosphate: Theory and Experiment Nicole Adelstein 1,3 , B. Simon Mun 4 , Hannah L. Ray 1,3 , Phillip N. Ross Jr. 1 , Jeffrey B. Neaton, 2 and Lutgard C. De Jonghe 1,3 1 Materials Sciences Division 2 Molecular Foundry Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley CA 94720, USA University of California at Berkeley, Berkeley CA 94720, USA 4 Department of Applied Physics Hanyang University, ERICA, Gyeonggi 426‐791 Republic of Korea Abstract Structural and electronic properties of cerium orthophosphate (CePO 4 ) are calculated using density functional theory (DFT) with the local spin‐density approximation (LSDA+U), with and without gradient corrections (GGA‐(PBE)+U), and compared to X‐ray diffraction and photoemission spectroscopy measurements. The density of states is found to change significantly as the Hubbard parameter U, which is applied to the Ce 4f states, is varied from 0 to 5 eV. The calculated structural properties are in good agreement with experiment and do not change significantly with U. Choosing U = 3 eV for LDSA provides the best agreement between the calculated density of states and the experimental photoemission spectra. I. Introduction New materials with high proton conductivities in the temperature range 300‐ 500°C can be of benefit as solid electrolytes in a variety of electrochemical devices such as hydrogen sensors, hydrogen separation membranes, and fuel cells. Incorporation of such a material into a fuel cell would, for example, facilitate the in­ situ reforming of liquid biofuels and reduce the need for noble catalysts. Rare‐earth phosphates have been investigated for this purpose because of their stability at high 3 Department of Materials Science and Engineering