Structurally Triggered Metal-Insulator Transition in Rare-Earth Nickelates

Rare-earth nickelates form an intriguing series of correlated perovskite oxides. Apart from LaNiO3, they exhibit on cooling a sharp metal-insulator electronic phase transition, a concurrent structural phase transition and a magnetic phase transition toward an unusual antiferromagnetic spin order. Appealing for various applications, full exploitation of these compounds is still hampered by the lack of global understanding of the interplay between their electronic, structural and magnetic properties. Here, we show from first-principles calculations that the metal-insulator transition of nickelates arises from the softening of an oxygen breathing distortion, structurally triggered by oxygen-octahedra rotation motions. The origin of such a rare triggered mechanism is traced back in their electronic and magnetic properties, providing a united picture. We further develop a Landau model accounting for the evolution of the metal-insulator transition in terms of the $R cations and rationalising how to tune this transition by acting on oxygen rotation motions.Comment: Submitted in Nature Communicatio

Can safety training contribute to enhancing safety?

International audienceTraining has always been an obvious response to any operational issue and safety issues are no exception. Further to an accident, training, and more specifically safety training, almost always forms part of the recommendations. More than that, safety training has always been considered by many as one of the major pillars for ensuring the safety of hazardous activities. This is the case in regulatory requirements as well as in many internal safety policies. Although this seems to make sense intuitively, intuition is not always of sound advice when it comes to safety. In reality, safety training conveys a number of implicit assumptions as to what contributes to making the operation of an organization safe. These assumptions, once made explicit, become debatable. However, unravelling them makes it possible to examine potential ways forward to reach beyond what seems to be the current safety training escalation dead-end