Additional Oxygen Ordering in "La2NiO4.25" (La8Ni4O17): II. Structural Features

摘要: Abstract On the basis of data obtained from refinement neutron diffraction experiments, structural features La 8 Ni 4 O 17 ("LaNiO 4.25 ") are discussed. It is shown that additional oxygen atoms in 2 layers form (O 5- 3 ) polyoxides including one delocalized hole. In NiO planes, a periodic modulation equatorial Ni-O distances characterizes various electronic configurations nickel cations and 2D charge density wave occurs, which more pronounced at low temperature than room temperature. A strong coupling between planes results transfer mechanisms, also account for stabilization monovalent (Ni + this compound. The formation —Ni -(O )-Ni )— chains along given 〈111〉 T directions correlated to interstitial ordering previously evidenced.