Microscopic stability mechanisms of a charge-ordered phase of La1.5Sr0.5NiO4

Using a pairwise potential approximation and a shell model, computer simula tion is performed of a charge-ordered crystal phase of La1.5Sr0.5NiO4, in w hich Ni2+ and Ni3+ ions are arranged in staggered rows in perovskite layers . This phase is found to be stable, and, in the process of its formation, t he contribution to the lowering of the total crystal energy from the charge rearrangement is smaller than that from the relaxation of the crystal stru cture (the structure of NiO2 layers, first of all) caused by this rearrange ment. The decrease in the total energy is due to the long-range Coulomb int eraction, predominantly the attraction between Ni3+ and oxygen ions in NiO2 layers. (C) 2000 MAIK "Nauka/Interperiodica".