authoren We have employed a range of atomistic simulation methods to explore aspects of defect chemistry in ABO3 (where A2+= Ba2+ or Sr2+, and B4+= Zr4+ or Hf4+) perovskites, placing emphasis on processes relevant for application of these materials as high performance scintillators. Specifically, we examined intrinsic defect reactions, A and B excess nonstoichiometry and the solution of Me3+ rare earth cations. As has been predicted in previous studies, we find that Schottky disorder is the lowest energy intrinsic process. For nonstoichiometry, we predict that AO‐excess is compensated by oxygen vacancies and BO2‐excess is charge compensated by A vacancies (see abstract figure). Finally, for Me3+ solution, we considered several reactions for Me3+ cations ranging in size from Lu3+ to La3+, and the preferred reaction depends on the specific Me3+ cation and whether or not phase separation occurs. Nonstoichiometry mechanisms in ABO3 perovskites. Red spheres correspond to O2−, blue to A2+, and green to B4+.

No abstract

Ab-initio simulations of a multi-component alloy using density functional theory (DFT) were combined with experiments on thin films of the same material using X-ray photoelectron spectroscopy (XPS) to study the...

Iron-based alloys are widely used as structural components in engineering applications. This calls for a fundamental understanding of their mechanical properties, including those of pure iron. Under operational temperatures the mechanical and magnetic properties will differ from those of ferromagnetic body-centeredcubic iron at 0 K. In this theoretical work we study the effect of disordered magnetism on the screw dislocation core structure and compare with results for the ordered ferromagnetic case. Dislocation cores control some local properties such as the choice of glide plane and the associated dislocation mobility. Changes in the magnetic state can lead to modifications in the structure of the core and affect dislocation mobility. In particular, we focus on the core properties of the 1 2 111 screw dislocation in the paramagnetic state. Using the noncollinear disordered local moment approximation to address paramagnetism, we perform structural relaxations within density functional theory. We obtain the dislocation core structure for the easy and hard cores in the paramagnetic state, and compare them with their ferromagnetic counterparts. By averaging the energy of several disordered magnetic configurations, we obtain an energy difference between the easy-and hard-core configurations, with a lower, but statistically close, value than the one reported for the ferromagnetic case. The magnetic moment and atomic volume at the dislocation core differ between paramagnetic and ferromagnetic states, with possible consequences on the temperature dependence of defect-dislocation interactions.