Growth of nano-domains in Gd–CeO₂ mixtures: hybrid Monte Carlo simulations

Abstract

Hybrid Monte Carlo (HMC) simulations are used to study the growth of Gd-rich domains in Gd doped CeO2, and we probe the conductivity of the resulting and other configurations by molecular dynamics.

Phase Transformations in the CeO2–Sm2O3 System: A Multiscale Powder Diffraction Investigation

“…Different kinds of aggregations were proposed, either involving few dopant atoms, as suggested by extended X-ray absorption fine structure (EXAFS) 9,10 and NMR, 11 or larger nanodomains tens of nanometers wide, as probed by electron microscopy 12,13 and atomic pair distribution function (PDF). 14,15 This picture was confirmed computationally only recently, 16,17 as the modeling of such big aggregates requires advanced computation strategies.…”

“…Different kinds of aggregations were proposed, either involving few dopant atoms, as suggested by EXAFS [9,10] and NMR [11], or larger nanodomains tens of nanometers wide, as probed by electron microscopy [12,13] and atomic Pair Distribution Function (PDF) [14,15]. This picture was confirmed computationally only recently [16,17], as the modeling of such big aggregates requires advanced computation strategies. In the case of Sm-doping, to which superior SOFCs performance among rare earth dopants are attributed [18,19], the conductivity drop is reported at critical concentration ranging from 0.15 [20], to 0.20 [21] and 0.25 [22].…”

Diffusion in gadolinium doped ceria thin films: a combined Monte Carlo and molecular dynamics study

“…50 Comparison of the diffusion coefficients with those calculated with a random distribution of dopant cations indicates that the influence of dopant-vacancy association is negligible and the thin films will not suffer from ageing in a similar manner to bulk materials. 5,46 The Monte Carlo simulations indicate that a tensile strain of 2 to 3 percent has little influence on the degree of segregation of dopant cations to both surfaces and interfaces.…”

“…This is in contrast to calculations performed on the bulk material where ordering of the Gd 3+ ions into nanodomains during the Monte Carlo simulations results in a reduction of the oxygen ion conductivity. 35,46 The greatest value of diffusion coefficients is for the FeO substrate (it is approximately 1.5 times greater than for the other substrates) and for the MnO substrate there is a similar value to that of MgO despite the increased spacing and the formation of dislocations in the thin film structure.…”

Molecular dynamics study of oxygen-ion diffusion in yttria-stabilized zirconia grain boundaries

“…To simulate this process via molecular dynamics, we require higher operating temperature since the simulation time will be a very small fraction of the experimental annealing time. [53][54][55][56] Therefore, the two surfaces have been put close together and then temperature was raised until we achieve complete amorphization of the structure without losing the short range order of each grain. The RDF was checked aer every few steps to make sure our sample is getting to the amorphous state.…”