Abstracts Biological Sciences

Molecular dynamics simulations of proton diffusion in yttrium doped barium zirconate

by Jakob Friman

Yttrium doped barium zirconate is a promising candidate as a proton conducting fuel cell electrolyte. Even if the mechanism behind proton conductivity is generally understood, the effects of dopants is a question that requires clarification. Recent studies suggests that dopants might act as traps for protons. An increased understanding of the behavior of protons in the vicinity of dopant atoms might contribute to the performance of future electrolytes. The aim of this thesis is to investigate the possibilities of studying proton diffusion with the means of molecular dynamics simulations, using the ReaxFF potential as the model for the inter atomic interactions. The work includes a study of the thermal expansion of yttrium doped barium zirconate, the diffusion of protons and how to obtain the self intermediate scattering function, which can be measured with neutron scattering experiments. The ReaxFF potential seems to provide a good model for studying proton diffusion in barium zirconate and it reproduces experimental results quite accurately. It is possible to obtain the self intermediate scattering function and study the motion of protons at different time and length scales. An exponential function, containing three parameters, where fitted to the obtained data. More investigations are required to interpret the data accurately, but some indication of the trapping effects of dopants can be seen.