β -Technetium: An allotrope with a nonstandard volume-pressure relationship

Le résumé fourni par la source

We report the synthesis and structure of the second allotrope of technetium, $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Tc}$. Transformative pathways are accessed at extreme conditions using the laser-heated diamond anvil cell and confirmed with in situ synchrotron x-ray diffraction and Raman spectroscopy. $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Tc}$ is fully recoverable to ambient conditions, although counter to our DFT calculations predicting a face-centered-cubic lattice, we observe a tetragonal structure $(I4/mmm)$ that exhibits further tetragonal distortion with pressure. $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Tc}$ has an expanded volume relative to the hcp ground state phase, that when doped with nitrogen has an unexpected volume lowering. Such anomalous behavior is possibly indicative of a rare electronic phase transition in a $4d$ element.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.