Related papers: Theory of Sodium Ordering in NaxCoO2
We report a first-principles projector augmented wave (PAW) study on Na$_{0.5}$CoO$_2$. With the sodium ion ordered insulating phase being identified in experiments, pure density functional calculations fail to predict an insulating ground…
The layered sodium cobalt oxide NaxCoO2 is studied by electron diffraction for a wide range of sodium contents, 0.15<x<0.75. An extensive series of ordered Na ion-Na vacancy superlattices is found beyond the simple hexagonal average…
The phase diagram of non-hydrated Na(x)CoO(2) has been determined by changing the Na content x using a series of chemical reactions. As x increases from 0.3, the ground state goes from a paramagnetic metal to a charge-ordered insulator (at…
The influence of electrostatic interactions on the ordering of sodium ions in Na$_x$CoO$_2$ is studied theoretically through Monte-Carlo simulations. For large $x$ small di- or tri-vacancy clusters are stable with respect to isolated Na…
The impact of oxygen deficiency on physical properties of Na2/3CoO2-x has been investigated. From the combined thermogravimetric, magnetic susceptibility and synchrotron X-ray Laue diffraction studies, it is demonstrated that Na2/3CoO2…
The impact of oxygen deficiency on physical properties of Na2/3CoO2-x has been investigated. From the combined thermogravimetric, magnetic susceptibility and synchrotron X-ray Laue diffraction studies, it is demonstrated that Na2/3CoO2…
We have synthesized and characterized different stable phases of sodium cobaltates Na$_{x}$CoO$_{2}$ with sodium content $0.65<x<0.80$. We demonstrate that $^{23}$Na NMR allows to determine the difference in the susceptibility of the phases…
Sodium ion ordering on in situ cleaved NaxCoO2 (x=0.84) surface has been studied by ultra high vacuum scanning tunneling microscopy (UHV-STM) at room temperature. Three main phases, with p(3x3), (root 7 x root 7), and (2 root 3 x 2 root 3)…
The CoO$_{2}$ layers in sodium-cobaltates Na$_{x}$CoO$_{2}$ may be viewed as a spin $S=1/2$ triangular-lattice doped with charge carriers. The underlying physics of the cobaltates is very similar to that of the high $T_{c}$ cuprates. We…
We investigate the electronic state of a CoO_2 plane in the layered cobalt oxides Na_xCoO_2 using the 11 band d-p model on a two-dimensional triangular lattice, where the tight-binding parameters are determined so as to fit the LDA band…
NaxCoO2 has emerged as a material of exceptional scientific interest due to the potential for thermoelectric applications, and because the strong interplay between the magnetic and superconducting properties has led to close comparisons…
We report $^{23}$Na and $^{59}$Co nuclear magnetic (NMR) and quadrupolar resonance (NQR) studies for the $x=2/3$ phase of the lamellar oxide Na$_{x}$CoO$_{2}$, which allowed us to establish reliably the atomic order of the Na layers and…
Charge ordering behavior is observed in the crystal prepared through the immersion of the $Na_{0.41}CoO_2$ crystal in distilled water. Discovery of the charge ordering in the crystal with Na content less than 0.5 indicates that the…
The electronic state in a CoO_2 plane of the layered cobalt oxides Na_{x}CoO_2 is investigated by using the 11 band d-p model on a two-dimensional triangular lattice, where the tight-binding parameters are determined so as to fit the LDA…
The structure of Na0.5CoO2, the low temperature insulator that separates the magnetic and superconducting regions in the NaxCoO2.yH2O phase diagram, is studied by high resolution powder neutron diffraction at temperatures between 10 and 300…
A series of CaxCoO2 (0.15 <= x <= 0.40) materials have been prepared by means of ion exchange reaction from NaxCoO2. Transmission electron microscopy (TEM) measurements revealed a rich variety of structural phenomena resulting from cation…
Charge ordering in doped \cob planes near the commensurate fillings $x = {1/4}$ and 1/3 are considered for $Na_x CoO_2.yH_2O$ and suggested to be competitors to superconductivity, leading to the experimentally seen narrow superconducting…
We have utilized neutron powder diffraction to probe the crystal structure of layered Na$_{x}$CoO$_{2}$ near the half doping composition of $x=$0.46 over the temperature range of 2 to 600K. Our measurements show evidence of a dynamic…
The strength and effect of Coulomb correlations in the (superconducting when hydrated) x~1/3 regime of Na(x)CoO(2) have been evaluated using the correlated band theory LDA+U method. Our results, neglecting quantum fluctuations, are: (1)…
We have synthesized and characterized four different stable phases of Na ordered Na$_{x}$CoO$_{2}$, for $0.65<x<0.8$. Above 100 K they display similar Curie-Weiss susceptibilities as well as ferromagnetic $q=0$ spin fluctuations in the…