Neutron diffraction study of nitride perovskite LaReN3

Abstract

Nitride perovskites ABN3 are extremely rare with only two known instances of bulk-phase materials, ThTaN3 and LaReN3. Here, we present a powder neutron diffraction study of the recently-reported nitride perovskite LaReN3. A full structural model of LaReN3 at 300 K ((Formula presented.), a=5.58523(5), b=5.59297(5), c=7.90419(6) Å, α=89.9170(8), β=90.1729(7), γ=90.1709(7)°) has been refined simultaneously against powder neutron and previously-collected synchrotron X-ray diffraction data. This indicates that the triclinic distortion is due to cooperative electronic distortions of ReN6 octahedra, and also demonstrates that all nitrogen positions are fully occupied so the sample is stoichiometric LaReN3. Lattice strains derived from fits to variable temperature powder neutron data from 5 to 300 K indicate that LaReN3 undergoes structural transitions to higher symmetry perovskite tilt structures between 300 and 350 K.