20.500.12556/RUL-187012 Structure of niobium to 365 GPa using ultrafast x-ray diffraction and shock compression 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. 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 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 true false true Angleški jezik Slovenski jezik Članek v reviji 2026-09-08 10:05:27 2026-09-08 10:05:31 2026-09-09 12:10:42 0000-00-00 00:00:00 2026 0 0 11 str. issue 15, art. 154101 Vol. 114 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 53:621.38 2469-9969 10.1103/tlxw-bfx4 290320643 Lonsdale_..._Structure.pdf Lonsdale_..._Structure.pdf 1 D0A6059092C219619BA5D2EEAAD77DE2 c351c0319190f11748be186b05e65861e5e658310f3d56c034ce2f066e41d356 56c1e5c5-ab5c-11f1-8bc5-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=246437 https://journals.aps.org/prb/abstract/10.1103/tlxw-bfx4 1 0bbf8fba-ab5c-11f1-8bc5-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=246435 Fakulteta za strojništvo 0 0 0