Structure of niobium to 365 GPa using ultrafast x-ray diffraction and shock compression

Lonsdale, C. M. (author), Trdan, Uroš (author)

The phase stability, crystal structure, and melting of Nb have been examined under high pressure shock compression to 365 GPa using ultrafast in situ x-ray diffraction measurements on two x-ray free electron laser facilities. On compression, Nb remains stable in the bcc phase up to 220 GPa, with coexistence of bcc-Nb and liquid from 249 to 298 GPa, and complete melting at 301 GPa, with melt identified by diffuse liquid diffraction. Melting initiates at higher pressure than expected based on theoretical predictions, and the data consistently excludes the presence of other suggested phases of Nb at these pressures, including Pnma and hcp, thereby resolving the long-standing structural discrepancy. Singh-type strength analysis provides experimental evidence for a change in sign of the elastic anisotropy parameter at 121 GPa, consistent with the previously reported heat-induced hardening to heat-induced softening transition in Nb.

• Language: English
• Keywords: synchrotron, X-ray free-electron laser (XFEL), in-situ X-ray diffraction (XRD), shock compression, laser-driven shock waves, velocity interferometer system for any reflector (VISAR), high-pressure phase transformations
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 11 str.
• Numbering: Vol. 114, issue 15, art. 154101
• PID: 20.500.12556/RUL-187012
• UDC: 53:621.38
• ISSN on article: 2469-9969
• DOI: 10.1103/tlxw-bfx4
• COBISS.SI-ID: 290320643
• Publication date in RUL: 08.09.2026

Record is a part of a journal

• Title: Physical review
• Shortened title: Phys. rev. B.
• Publisher: American Physical Society
• ISSN: 2469-9969
• COBISS.SI-ID: 3042148

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: sinhrotron, rentgenski laser na proste elektrone (XFEL), in-situ rentgenska difrakcija (XRD), udarna kompresija, lasersko generirani udarni valovi, hitrostni interferometer za poljubni reflektor (VISAR), visokotlačne fazne transformacije