Temperature dependence of the local structure and lattice dynamics of wurtzite-type ZnO

Abstract

Temperature-dependent (10-300 K) Zn K-edge EXAFS spectra for polycrystalline wurtzite-type ZnO were analysed using ab initio multiple-scattering theory and taking into account anisotropy of the crystallographic structure and thermal disorder. We employed two different simulation approaches: classical molecular dynamics (MD) and reverse Monte Carlo coupled with evolutionary algorithm (RMC/EA method). The accuracy of several forcefield models, which are commonly used in the MD simulations of bulk and nanostructured ZnO, was tested based on a comparison between the experimental and simulated Zn K-edge EXAFS spectra. It was found that available force-field models fail to describe accurately many-atom distribution functions. More accurate solution was obtained by the RMC/EA method, which allowed us also to resolve the non-equivalent groups of atoms in the first two coordination shells around absorbing Zn atom and to follow the changes of structural parameters with temperature variation. It was found that upon increasing temperature the structure of ZnO becomes more anisotropic due to the increase of internal parameter u of the oxygen Wyckoff position (2b) and related Zn 0 -O 2 distances.

Linking the evolution of catalytic properties and structural changes in copper–zinc nanocatalysts using operando EXAFS and neural-networks

“…No generally applicable empirical force-eld model, however, exists for oxides and other covalent materials, due to the signicantly more complex and strongly directional nature of the chemical bond in these materials. In some specic cases, such as wurtzite-type ZnO and rocksalt-type NiO, an accurate description of the materials structure and dynamics can be achieved in MD with Buckingham-type potentials, and, consequently, theoretical EXAFS spectra can be generated that, as we have demonstrated, [54][55][56][57][58][59] match well the corresponding experimental data.…”

Thermal disorder and correlation effects in anti-perovskite-type copper nitride

“…The obtained detailed information on the temperature dependence of local atomic and dynamic structure of Cu 3 N provides a background for the development of its theoretical model, based on ab-initio or force-field molecular dynamics methods. We have shown previously [73,74] that EXAFS data are well suited for such model validation.…”

Probing structural relaxation in nanosized catalysts by combining EXAFS and reverse Monte Carlo methods

“…The feasibility of RMC/EA approach for EXAFS data analysis have been recently demonstrated by us in studies of bulk crystalline oxide materials [35,36] and in studies of nanostructured tungstates with very small nanocrystalites consisting of just a few coordination polyhedra [37]. Here for the first time we apply this approach to studies of structure in strained metal nanoparticles, with the aim to recover and investigate the asymmetric distributions of interatomic distances.…”