Speaker
Prof.
Evgeny Alekseev
(Forschungszentrum Jülich)
Description
Using extreme pressure (10GPa/1200°C) we obtained a new modification of U2O5 with an extraordinary dense structure. The crystal structure of resulting HP (high pressure)-U2O5 is dramatically differs from ambient pressure polymorph so called delta-U2O5. The structure of HP-U2O5 is more related to the cubic UO2 than to the layered delta-U2O5. Using state of the art ab initio methods we reveal the stability ranges of both ambient and high pressure forms of U2O5 and demonstrated a potential pathway of phase transition under pressure.
In second case we demonstrated that the pentavalent uranium (U(V)) can be stabilized in [Ln(UVO2)W4O14] (Ln = Nd-Tm and Y) series via aliovalent substitution of Ca2+ cations. We confirmed U(V) stabilization using state of the art methods such as U M4 edge high energy resolution X-ray absorption near edge structure (HR-XANES).Magnetic study reveals low temperature ordering of 5f1 and 4fn systems. All the phases tend to demonstrate the antiferromagnetic properties with significant difference between pure 5f1 system (Y-beating phase) and 5f1-4fn compounds (Nd-Tm).
Primary author
Prof.
Evgeny Alekseev
(Forschungszentrum Jülich)
