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Nb-H system at high pressures and temperatures

DOI: 10.1103/PhysRevB.95.104110 DOI Help

Authors: Guangtao Liu (Jilin University; Max Planck Institute for Chemistry; China Academy of Engineering Physics) , Stanislav Besedin (Max Plank Institute for Chemistry) , Alla Irodova (National Research Centre “Kurchatov Institute,” Moscow) , Hanyu Liu (Carnegie Institution of Washington) , Guoying Gao (Yanshan University) , Mikhail Eremets (Max Planck Institute for Chemistry) , Xin Wang (Jilin University) , Yanming Ma (Jilin University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 95

State: Published (Approved)
Published: March 2017
Diamond Proposal Number(s): 8284 , 9745

Abstract: We studied the Nb-H system over extended pressure and temperature ranges to establish the highest level of hydrogen abundance we could achieve from the resulting alloy. We probed the Nb-H system with laser heating and x-ray diffraction complemented by numerical density functional theory-based simulations. New quenched double hexagonal close-packed (hcp) NbH2.5 appears under 46 GPa, and above 56 GPa cubic NbH3 is formed as theoretically predicted. Nb atoms are arranged in close-packed lattices which are martensitically transformed in the sequence: face-centered cubic (fcc) → hcp → double hcp (dhcp) → distorted body-centered cubic (bcc) as pressure increases. The appearance of fcc NbH2.5−3 and dhcp NbH2.5 cannot be understood in terms of enthalpic stability, but can be rationalized when finite temperatures are taken into account. The structural and compressional behavior of NbHx>2 is similar to that of NbH. Nevertheless, a direct H-H interaction emerges with hydrogen concentration increases, which manifests itself via a reduction in the lattice expansion induced by hydrogen dissolution.

Subject Areas: Materials, Physics

Instruments: I15-Extreme Conditions

Other Facilities: Deutsches Elektronen-Synchrotron (DESY)