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Citation: P. Broqvist, J. Kullgren, M.J. Wolf, A.C.T. van Duin, and K. Hermansson (2015), "ReaxFF Force-Field for Ceria Bulk, Surfaces, and Nanoparticles", The Journal of Physical Chemistry C, 119(24), 13598-13609. DOI: 10.1021/acs.jpcc.5b01597.
Abstract: We have developed a reactive force-field of the ReaxFF type for stoichiometric ceria (CeO2) and partially reduced ceria (CeO2–x). We describe the parametrization procedure and provide results validating the parameters in terms of their ability to accurately describe the oxygen chemistry of the bulk, extended surfaces, surface steps, and nanoparticles of the material. By comparison with our reference electronic structure method (PBE+U), we find that the stoichiometric bulk and surface systems are well reproduced in terms of bulk modulus, lattice parameters, and surface energies. For the surfaces, step energies on the (111) surface are also well described. Upon reduction, the force-field is able to capture the bulk and surface vacancy formation energies (Evac), and in particular, it reproduces the Evac variation with depth from the (110) and (111) surfaces. The force-field is also able to capture the energy hierarchy of differently shaped stoichiometric nanoparticles (tetrahedra, octahedra, and cubes), and of partially reduced octahedra. For these reasons, we believe that this force-field provides a significant addition to the method repertoire available for simulating redox properties at ceria surfaces.

Notes: J. Kullgren included the following notes: "Usage: The parameters have been tested for static calculations of CeO2 and partially reduced CeO(2-x) using the LAMMPS code with the fortran implementation of reaxFF. For energy comparisons, use the in-cell approach (see the paper) when calculating reaction energies. Note to the users: After publication we have made further use of the published ceria parameters and noticed an additional (false) local minimum occurring for partially reduced ceria at a short Ce-O distance (approx. 1.89 Angstrom). This may (for example) have consequences for dynamic simulations at moderate temperatures. Our attempts to heal this deficiency have so far destroyed the good performance regarding the ordering of the surface vacancy energies on the (111) surface. In relevant cases, we advice our users to analyze the bond distances from the simulations."

ReaxFF (2015--Broqvist-P--Ce-O--LAMMPS--ipr1)
Notes: This file was sent by J. Kullgren (Uppsala University) on 19 December 2016 and posted with his permission.
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Date Created: October 5, 2010 | Last updated: October 02, 2018