Possible Peierls Distortion Through Re ₂ Dimer Formation in the LaNiO ₂ ‐Type Nitrides <i>Ln</i> ReN ₂ ( <i>Ln</i> = Pr, Nd)

Abstract

Abstract Nitride perovskites are a recently opened class of materials with a limited number of stable compounds. Notably, anion‐vacancy‐ordered materials such as LaNiO 2 ‐type nitrides are rare despite useful properties such as superconductivity reported for analogous oxides. Here, we report the preparation of two Ln ReN 2 ( Ln  = Pr, Nd) materials with a distorted LaNiO 2 ‐type structure at high‐pressure, high‐temperature conditions of a large volume press. Powder X‐ray and neutron diffraction show that the orthorhombic distortion (o‐ Ln ReN 2 ) of the LaNiO 2 ‐aristotype structure is caused by buckling of the ReN 4/2 layers through Re dimerization. Electronic structure analysis reveals that the o‐ Ln ReN 2 materials are composed of classic nitridometallate anions and a cationic intermetallic framework. Moreover, the calculations reveal the driving force of the Re dimerization likely to be from an electronic instability related to a Peierls‐type distortion. We further characterize the magnetic ground state of both materials with magnetization measurements as well as magnetic neutron scattering uncovering a long‐range antiferromagnetic order of Nd 3+ moments in NdReN 2 at T N  = 15.5 K. The stability of the compounds is investigated by temperature‐dependent powder X‐ray diffraction showing decomposition of NdReN 2 at ca. 750 °C. The o‐ Ln ReN 2 materials represent a curious class of nitrides at the border of classic nitridometallates, intermetallics, and low‐dimensional complex chemistry.