Formation of the cerium orthovanadateCeVO4:DFT+Ustudy

Abstract

We report density functional theory calculations of the structural, electronic, and thermodynamic properties of cerium orthovanadate CeVO4 employing the local density approximation LDA , generalized gradient approximation GGA-PBE , LDA+U, and GGA-PBE+U functionals. The LDA+U, GGA-PBE+U, LDA, and GGA-PBE equilibrium volumes deviate by −2.4%, +3.6%, −7.4%, and −0.8%, respectively, from experimental results. DFT+U DFT predicts an antiferromagnetic ferromagnetic insulating metallic ground state, which is in agreement with experimental observations. DFT+U yields Ce and V ions in the III+ and V+ oxidation state, respectively. CeVO4 can be obtained by the reaction between Ce2O3 and V2O5 1 2Ce2O3 s + 1 2V2O5 s →CeVO4 s under an inert atmosphere, which is described as exoenergetic H0 =1.6−1.8 eV by all functionals. The reaction 1 2Ce2O3 s + 1 2V2O5 s →CeO2 s +VO2 s is exoenergetic with H0 =0.75, 0.25, 1.70, and 1.24 eV for LDA+U, GGA-PBE+U, LDA, and GGA-PBE, respectively. Hence, VV+ is more easily reduced to VIV+ than CeIV+ to CeIII+, but the difference is small as obtained with DFT+U, PBE+U, in particular. The variation of this reaction energy is due to the different performance of the various approaches for the description of the change in oxidation state of cerium, IV+ to III+ J. L. F. Da Silva et al., Phys. Rev. B 75, 045121 2007 . The small difference between the VV and CeIV reducibilities may have consequences for the use of CeO2 as support of V2O5 catalysts in selective oxidation.