Narrow Results

Nd₂CuO${}_{4\pm \delta }$ is known to possess either oxygen vacancies or interstitial oxygen defects, depending on the synthesis route, as well as may exhibit the A-site deficiency. In this work, insight into physicochemical properties of Nd₂CuO${}_{4\pm \delta }$ and Nd${}_{1.9}$CuO${}_{4\pm \delta }$ layered oxides is given, focusing on the crystal structure, electrical conductivity, and oxygen permeation, as well as on numerical density functional theory (DFT) simulations concerning ionic defects formation and their possible movement in the crystal structure. The results indicate that in oxidizing conditions at low temperatures, interstitial oxygen defects are stable, but with the increase of temperature, the release of oxygen is observed, leading to formation of the oxygen vacancies. Both materials are stable at elevated temperatures in air and Ar. Larger oxygen nonstoichiometry and improved electrical conductivity at high temperatures for Nd${}_{1.9}$CuO${}_{4\pm \delta }$ compound are accompanied by the recorded oxygen flux of ca. 0.2mLcm${}^{-2}$min${}^{-1}$ at 880^∘C for 0.8mm thick ceramic membrane.

New technologies deeply depend on the ability of chemists to synthesize new functional materials. However, this synthetic step requires great efforts. Moreover, it is very likely that the ensuing compound does not fit the expected properties. With the advent of simulation, associated with the increase in computer performance and efficiency of codes, a screening of the best potential candidates to be synthesized becomes available. Accordingly, getting a polymer with a specific permeability, and also understanding the molecular reasons underlying this process, are some of the assets of molecular simulation. Nevertheless, representation of a material from a molecular perspective is not straightforward. A specific protocol must be established. It takes into account the fact that calculations are carried out on very tiny systems. An accurate depiction and perpetual validations confronting simulated results with experimental data make the protocol relevant. The computation of the penetrants’ diffusion coefficient and solubility is then introduced, in order to reveal the simulation of the permeation of a small molecule through an amorphous polymer system. The paper concludes with the most recent studies on the subject.