Ab initio calculation of the attempt frequency of oxygen diffusion in pure and samarium doped ceria.

Title Ab initio calculation of the attempt frequency of oxygen diffusion in pure and samarium doped ceria.
Authors J. Koettgen; T. Zacherle; S. Grieshammer; M. Martin
Journal Phys Chem Chem Phys
DOI 10.1039/c6cp04802a
Abstract

The rate of oxygen ion jumps in a solid oxide depends not only on the activation energy but also on the pre-exponential factor of diffusion. In order to allow a fully ab initio prediction of the oxygen ion conductivity in pure and samarium doped ceria, we calculated the attempt frequency for an oxygen ion jump from first principles combining DFT+U, the NEB method, phonon calculations and the transition state theory. Different definitions of the jump attempt frequency are presented. The equivalence of the Eyring and the Vineyard method is shown without restriction to the Gamma point. Convergence checks of the phonon mesh reveal that the common reduction to the Gamma point is not sufficient to calculate the attempt frequency. Calculations of Sm doped ceria revealed an increase of the prefactor. The attempt frequency for the constant pressure case in quasi-harmonic approximation is larger than the attempt frequency at constant volume in harmonic approximation. The calculated electronic energies, enthalpies and entropies of migration are in agreement with the experimental diffusion coefficients and activation energies.

Citation J. Koettgen; T. Zacherle; S. Grieshammer; M. Martin.Ab initio calculation of the attempt frequency of oxygen diffusion in pure and samarium doped ceria.. Phys Chem Chem Phys. 2017;19(15):99579973. doi:10.1039/c6cp04802a

Related Elements

Samarium

62 Sm 150.360000000 Samarium

See more Samarium products. Samarium (atomic symbol: Sm, atomic number: 62) is a Block F, Group 3, Period 6 element with an atomic radius of 150.36. Samarium Bohr ModelThe number of electrons in each of samarium's shells is 2, 8, 18, 24, 8, 2 and its electron configuration is [Xe]4f6 6s2. The samarium atom has a radius of 180 pm and a Van der Waals radius of 229 pm. In its elemental form, samarium has a silvery-white appearance. Elemental Samarium PictureSamarium is not found as free element in nature. It is found in the minerals cerite, gadolinite, samarskite, monazite and bastnäsite. Samarium is classified as a rare earth element and is the 40th most abundant element in the Earth's crust. Samarium was discovered and first isolated by Lecoq de Boisbaudran in 1879. It is named after the mineral samarskite, the mineral from which it was isolated.

Cerium

58 Ce 140.116000000 Cerium

See more Cerium products. Cerium (atomic symbol: Ce, atomic number: 58) is a Block F, Group 3, Period 6 element with an atomic weight of 140.116. The number of electrons in each of cerium's shells is 2, 8, 18, 19, 9, 2 and its electron configuration is [Xe]4f2 6s2. Cerium Bohr ModelThe cerium atom has a radius of 182.5 pm and a Van der Waals radius of 235 pm. In its elemental form, cerium has a silvery white appearance. Cerium is the most abundant of the rare earth metals. It is characterized chemically by having two valence states, the +3 cerous and +4 ceric states. The ceric state is the only non-trivalent rare earth ion stable in aqueous solutions. Elemental CeriumIt is therefore strongly acidic and oxidizing, in addition to being moderately toxic.The cerous state closely resembles the other trivalent rare earths. Cerium is found in the minerals allanite, bastnasite, hydroxylbastnasite, monazite, rhabdophane, synchysite and zircon. Cerium was discovered by Martin Heinrich Klaproth, Jöns Jakob Berzelius, and Wilhelm Hisinger in 1803 and first isolated by Carl Gustaf Mosander in 1839. The element was named after the asteroid Ceres, which itself was named after the Roman god of agriculture.

Related Forms & Applications

Oxides
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