Abstract

To resolve a dispute associated with the ferroelectricity in hexagonal InMnO3 (h-IMO), we have examined the ground-state structure by exploiting density-functional theory calculations. It is shown that the ferroelectric $\textit{P}6_{3}\textit{cm}$  phase is marginally stable over the nonpolar $\textit{P}\bar{3}\textit{c}1$  phase for a wide range of the external pressure. However, the computed Kohn-Sham energy predicts an interesting crossover from the polar $\textit{P}6_{3}\textit{cm}$  state to the nonpolar $\textit{P}\bar{3} \textit{c}1$  state beginning at a compressive strain of ~1%. The partial density of states (PDOS) supports our previous finding that the In 4d-O 2p hybridization is the main bonding mechanism directly related to the manifestation of ferroelectricity in h-IMO. In addition, the computed PDOS does not show any evidence of the In 5s-O 2p orbital overlapping which had been asserted to be the main bonding interaction in the nonpolar $\textit{P}\bar{3}\textit{c}1$  phase.