2018/03/31 by Dawei Zhou, Zhou, Dawei, Jiahui Yu +7 · 3 citations
Chemistry · Earth and Planetary Sciences · Materials Science · Mathematics · Physics and Astronomy · #Atomic physics #Chemistry #Computational Physics (physics.comp-ph) #Crystallography #Diagram #FOS: Physical sciences #Ground state #High pressure #High-pressure geophysics and materials #Materials Science (cond-mat.mtrl-sci) #Materials science #Mathematics #Metallurgy #Nanotechnology #Nitride #Nuclear Materials and Properties #Phase (matter) #Phase diagram #Physical chemistry #Physics #Radioactive element chemistry and processing #Stoichiometry #Structural stability #Thermodynamics #Uranium #Zigzag #cond-mat.mtrl-sci #physics.comp-ph
paper · pdf · doi:10.48550/arxiv.1804.00095
published in arXiv (Cornell University) (Cornell University) · 25pages, 8 figures
arxiv created 2018/03/31 · openalex publication_date 2018/03/31 · arxiv updated 2018/04/03 · openalex created_date 2018/04/13 · openalex updated_date 2026/07/28
Uranium nitrides have been the subject of intense research owing to their potential applications as advanced nuclear fuels. However, the phase diagram of the U-N system at low temperature and high pressure still remains unclear. In this paper, we explore extensively the phase diagram of the U-N system up to 150 GPa based on first-principles swarm structure searches. The phase diagrams of the experimentally known stoichiometries like U2N3 and UN2 are refined. At zero temperature and pressure, the experimentally observed CaF2-type UN2 is found to transform into another new I41/amd-type UN2, which is related to the dynamical instability originated from Peierls mechanism. Two new stable high-pressure phases of U2N3 and UN2 are identified for the first time. Besides, several new chemical stoichiometries (UN4, UN3, U3N5 and U2N) are found to have stability fields on the U-N phase diagram. The pressure-induced phase transitions for the U-N system are further investigated. The peculiar structural features such as N2-dimers, planar SO3-like N(N)3 units, non-coplarnar zigzag N4 units, and zigzag U chains are found in U-N compounds under pressure. Our results on the structure exploring provide a better understanding of the structural characteristics and physical properties of uranium nitrides under pressure.