title: Ground-state phase diagram of Na(x)CoO(2): correlation of Na ordering with CoO(2) stacking sequences.
abstract: We have proposed a Hamiltonian that takes into account both Na-Na interactions and coupling between Na ions and CoO(2) layers. By a combination of the Monte Carlo and first-principles approaches, all the possible stacking sequences of CoO(2) layers together with the Na ordering have been obtained. In particular, an infinite series of ground states of Na ordering has been predicted in P3-Na(x)CoO(2). We have obtained the ground-state phase diagram with the variation of Na concentration, which explains well the complex variation of the CoO(2) stacking sequences. Our calculations show that the ordering of Na ions to minimize the Coulomb interaction is the main cause of the variation of the CoO(2) stacking sequences.
authors.affiliation: Department of Physics and Key Laboratory of Atomic and Molecular Nanoscience (Ministry of Education), Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Yanli
authors.initials: Y
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Ding
authors.forename: Jun
authors.initials: J
authors.lastname: Ni