Pauli-paramagnetic and metallic properties of high pressure polymorphs of BaRhO3 oxides containing Rh2O9 dimers

Abstract

From our material exploration study in wide pressure and temperature conditions, we found a new 6H polymorph of BaRhO₃ was stabilised under high pressure conditions from 14 to 22 GPa. The material crystallised in the monoclinic 6H hexagonal perovskite structure in space group C2/c. The 4H BaRhO₃ polymorph was stabilised at lower pressures, but the 3C cubic BaRhO₃ likely requires pressures greater than 22 GPa. Both 6H and 4H polymorphs contain Rh₂O₉ dimers and the large 4d Rh orbital spatial diffusivity in these dimers leads to Pauli paramagnetic and metallic ground states, which are also supported by first-principles electronic structure calculations. High Wilson ratios of approximately 2 for either compound indicate strong electron correlation.