Analysis of Orbital Hybridization in the Magnetoelectric ${\hbox{YMnO}}_{3}$ Crystal From First Principles Calculations

We performed first-principles band-structure calculations on multiferroic hexagonal
${\hbox{YMnO}}_{3}$
to study the characteristics of Mn-O and Y-O chemical bonds in the vicinity of ferroelectric (FE)—paraelectric (PE) phase transition. Both the FE and the PE crystal structures were successfully reproduced and considered paramagnetic ones. Exchange-correlation effects between electrons were treated by the recently developed modified Becke-Johnson (mBJ) approach which enabled successful reproduction of experimental band gap in the FE phase and predicted a small band gap in the PE phase. Analysis of the resulting electronic structures in both phases indicates that Mn-O bonds do not suffer significant changes during the PE-FE phase transition, while the Y-O bonds become more covalent, with clear signs of hybridization between Y
$4{\rm d}_{\rm z}^{2}$
and the O
${\rm p}_{\rm z}$
orbitals.