Experimental and theoretical confirmation of an orthorhombic phase transition in niobium at high pressure and temperature

Errandonea, D ORCID: https://orcid.org/0000-0003-0189-4221, Burakovsky, L ORCID: https://orcid.org/0000-0002-7428-8604, Preston, DL, MacLeod, SG ORCID: https://orcid.org/0000-0002-1055-2576, Santamaría-Perez, D, Chen, S, Cynn, H ORCID: https://orcid.org/0000-0003-4658-5764, Simak, SI, McMahon, MI, Proctor, JE ORCID: https://orcid.org/0000-0003-3639-8295 and Mezouar, M ORCID: https://orcid.org/0000-0001-5336-544X 2020, 'Experimental and theoretical confirmation of an orthorhombic phase transition in niobium at high pressure and temperature' , Communications Materials, 1 , p. 60.

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Abstract

Compared to other body-centered cubic (bcc) transition metals, Nb has been the subject of fewer compression studies and there are still aspects of its phase diagram which are unclear. Here, we report a combined theoretical and experimental study of Nb under high pressure and temperature. We present the results of static laser-heated diamond anvil cell experiments up to 120 GPa using synchrotron-based fast x-ray diffraction combined with ab initio quantum molecular dynamics simulations. The melting curve of Nb is determined and evidence for a solid-solid phase transformation in Nb with increasing temperature is found. The high-temperature phase of Nb is orthorhombic Pnma. The bcc-Pnma transition is clearly seen in the experimental data on the Nb principal Hugoniot. The bcc-Pnma coexistence observed in our experiments is explained. Agreement between the measured and calculated melting curves is very good except at 40–60 GPa where three experimental points lie below the theoretical melting curve by 250 K (or 7%); a possible explanation is given.

Item Type:	Article
Schools:	Schools > School of Computing, Science and Engineering > Salford Innovation Research Centre
Journal or Publication Title:	Communications Materials
Publisher:	Nature Publishing Group
ISSN:	2662-4443
Related URLs:	Publication
Funders:	Spanish Ministerio de Ciencia, Innovación y Universidades, Generalitat Valenciana
Depositing User:	JE Proctor
Date Deposited:	14 Sep 2020 12:51
Last Modified:	16 Feb 2022 05:40
URI:	https://usir.salford.ac.uk/id/eprint/58284

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