Ab initio study of the charge order and Zener polaron formation in half-doped manganites

has been addressed with quantum chemicalcalculations on large embedded clusters. We find a charge ordered state for the crystal structure reported byRadaelli et al. [Phys. Rev. B 55, 3015 (1997)] and Zener polaron formation in the crystal structure withequivalent Mn sites proposed by Daoud-Aladineet al. [Phys. Rev. Lett. 89, 097205 (2002)]. Important O toMn charge transfer effects are observed for the Zener polaron.DOI: 10.1103/PhysRevB.70.235104 PACS number(s): 75.47.Lx, 71.15.Ap, 71.27.1aI. INTRODUCTION