title: Oxygen stripes in La0.5Ca0.5MnO3 from ab initio calculations.
abstract: We investigate the electronic, magnetic, and orbital properties of La0.5Ca0.5MnO3 perovskite by means of an ab initio electronic structure calculation within the Hartree-Fock approximation. Using the experimental crystal structure reported by Radaelli et al. [Phys. Rev. B 55, 3015 (1997)]], we find a charge-ordering stripelike ground state. The periodicity of the stripes, and the insulating magnetic structure, consisting of antiferromagnetically coupled zigzag chains, are in agreement with neutron x-ray and electron diffraction experiments. However, the detailed structure is more complex than that envisaged by simple models of charge and orbital order on Mn d levels alone, and is better described as a charge-density wave of oxygen holes, coupled to the Mn spin/orbital order.
authors.affiliation: Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK.
authors.forename: V
authors.initials: V
authors.lastname: Ferrari
authors.forename: M
authors.initials: M
authors.lastname: Towler
authors.forename: P B
authors.initials: PB
authors.lastname: Littlewood