Density functional theory studies of structural distortion in lone pair substituted LuMnO3

Structural distortion and electronic structure calculations of lone pair (As, Sb and Bi) substituted orthorhombic LuMnO3 have been carried out using density functional theory (DFT) method. We find from our calculations that substitution of lone pair cations at the A-site of LuMnO3 with specific lone pair cation/Lu ordering breaks the two-fold rotational symmetry of orthorhombic LuMnO3 and alters drastically both the A-O and MnO- bond interactions. Despite these structural changes, E-type antiferromagnetic (E-AFM) ordering is retained in lone pair substituted compounds. Furthermore, modifications in local structure leads to the formation of two different Mn sites (Mn' and Mn") with distinct local structure around them, inducing diametric Jahn-Teller (JT) distortion. As a consequence, significant variation in the Mn'-O and Mn"O- bond distribution arises, which seemed to influence electronic polarization appreciably.