Flourite-type nanocrystalline Ce0.9Fe0.1O2−δ and Ce0.89Fe0.1Pd0.01O2−δ solid solutions have been synthesized by solution combustion method, which show higher oxygen storage/release property (OSC) compared to CeO2 and Ce0.8Zr0.2O2. Temperature programmed reduction and XPS study reveal that the presence of Pd ion in Ce0.9Fe0.1O2−δ facilitates complete reduction of Fe3+ to Fe2+ state and partial reduction of Ce4+ to Ce3+ state at temperatures as low as 105 °C compared to 400 °C for monometal-ionic Ce0.9Fe0.1O2−δ. Fe3+ ion is reduced to Fe2+ and not to Fe0 due to favorable redox potential for Ce4+ + Fe2+ → Ce3+ + Fe3+ reaction. Using first-principles density functional theory calculation we determine M−O (M = Pd, Fe, Ce) bond lengths, and find that bond lengths vary from shorter (2.16 Å) to longer (2.9 Å) bond distances compared to mean Ce−O bond distance of 2.34 Å for CeO2. Using these results in bond valence analysis, we show that oxygen with bond valences as low as −1.55 are created, leading to activation of lattice oxygen in the bimetal ionic catalyst. Temperatures of CO oxidation and NO reduction by CO/H2 are lower with the bimetal-ionic Ce0.89Fe0.1Pd0.01O2−δ catalyst compared to monometal-ionic Ce0.9Fe0.1O2−δ and Ce0.99Pd0.01O2−δ catalysts. From XPS studies of Pd impregnated on CeO2 and Fe2O3 oxides, we show that the synergism leading to low temperature activation of lattice oxygen in bimetal-ionic catalyst Ce0.89Fe0.1Pd0.01O2−δ is due to low-temperature reduction of Pd2+ to Pd0, followed by Pd0 + 2Fe3+ → Pd2+ + 2Fe2+, Pd0 + 2Ce4+ → Pd2+ + 2Ce3+ redox reaction.

We report interesting anomalies in the temperature dependent Raman spectra of FeSe 0.82 measured from 3K to 300K in the spectral range from 60 to 1800 cm -1 and determine their origin using complementary first-principles density functional calculations. A phonon mode near 100 cm -1 exhibits a sharp increase by ~ 5% in frequency below a temperature T s (~ 100K) attributed to strong spin-phonon coupling and onset of shortrange antiferromagnetic order. In addition, two high frequency modes are observed at 1350 cm -1 and 1600 cm -1 , attributed to electronic Raman scattering from (x 2 -y 2 )to xz / yz d-orbitals of Fe.

The chimera state with co-existing coherent-incoherent dynamics has recently attracted a lot of attention due to its wide applicability. We investigate non-locally coupled identical chaotic maps with delayed interactions in the multiplex network framework and find that an interplay of delay and multiplexing brings about an enhanced or suppressed appearance of chimera state depending on the distribution as well as parity of delay values in the layers. Additionally, we report a layer chimera state with an existence of one layer displaying coherent and another layer demonstrating incoherent dynamical evolution. The rich variety of dynamical behavior demonstrated here can be used to gain further insight into the real-world networks which inherently possess such multi-layer architecture with delayed interactions.

Combining transmission electron microscopes and density functional theory calculations, we report the nucleation and growth mechanisms of room temperature rolling induced face-centered cubic titanium (fcc-Ti) in polycrystalline hexagonal close packed titanium (hcp-Ti). Fcc-Ti and hcp-Ti take the orientation relation: 〈0001〉hcp||〈001〉fcc and , different from the conventional one. The nucleation of fcc-Ti is accomplished via pure-shuffle mechanism with a minimum stable thickness of three atomic layers, and the growth via shear-shuffle mechanisms through gliding two-layer disconnections or pure-shuffle mechanisms through gliding four-layer disconnections. Such phase transformation offers an additional plastic deformation mode comparable to twinning.

Twinning-associated boundaries (TB), f1 0 1 ng coherent twin boundaries (CTB) and the coherent basal-prismatic (CBP) boundary in six hexagonal metals (Cd, Zn, Mg, Zr, Ti and Be) are studied using first-principles density function theory, with the focus on the structural character of TB and the solute's solubility at TB. Regarding the structure and energy of TB, the formation of TB is associated with the creation of an excess volume. All six metals show positive excess volume associated with ð1 0 1 1Þ and ð1 0 1 3Þ CTB, but the excess volume associated with ð1 0 12Þ CTB and CBP can be positive or negative, depending on the metal. The ð1 0 1 2Þ CTB has higher excess energy than ð1 0 1 1Þ and ð1 0 1 3Þ CTB for metals with c=a < ffiffiffiffiffiffiffi ffi 8=3 p , but lower for metals with c=a > ffiffiffiffiffiffiffi ffi 8=3 p . More interestingly, CBP has lower excess energy than ð1 0 1 2Þ CTB for all metals. This is consistent with the recent finding concerning the pure-shuffle nucleation mechanism of ð1 0 1 2Þ twins. To understand solubility at TB, the solubility of solute atoms in Mg, Ti and Zr is calculated for solute positions in bulk, ð1 0 1 2Þ CTB and CBP boundaries. In general, solute atoms have better solubility at CTB and CBP than in bulk. Interestingly, the solubility of solute atoms changes linearly with normal strain at CBP, increasing with normal strain for solute atoms with a greater metallic radius than the matrix, and decreasing with normal strain for solute atoms with a smaller metallic radius than the matrix. This suggests that the distribution of solute atoms in bulk, CTB and CPB boundaries varies with stress state and, in turn, affects the mobility of TB.

Experiments were conducted on concentrated suspensions of neutrally buoyant particles which exhibit negative dielectrophoresis. We found that, due to interparticle electrical interactions, such suspensions undergo a phase separation when subjected to a high-gradient ac field (approximately kV/mm) and form a propagating distinct front between the regions enriched with and depleted of particles. A generalization of our theory for the thermodynamics of the field-induced phase transitions in suspensions of polarized particles [Phys. Rev. E 52, 1669 (1995); 54, 5428 (1996); 60, 3015 (1999)] is proposed for the front propagation, and its predictions are shown to be consistent with the experiments even though the model contains no fitting parameters. The combination of field-induced dielectrophoresis and phase transition provides a method for strongly concentrating particles in prespecified regions of dielectrophoretic devices.

We report the discovery of a new class of an electric field-driven bulk phase transition due solely to dipolar interactions in a suspension under the action of a uniform ac field where the effects of other competing forces are suppressed. This transition appears after the well-known chain-column formation and causes the uniform suspension of columns to rearrange into a cellular pattern consisting of particle-free domains surrounded by particle-rich walls. Interestingly, the characteristic size of these domains scales linearly with the interelectrode spacing and remains insensitive to the size of the particles.

The structure and properties of the 1:1 superlattice of LaVO3 and SrVO3 are investigated with a firstprinciples density-functional-theory-plus-U (DFT+U ) method. The lowest energy states are antiferromagnetic charge-ordered Mott-insulating phases. In one of these insulating phases, layered charge ordering combines with the layered cation ordering to produce a polar structure with nonzero spontaneous polarization normal to the interfaces. This polarization is produced by electron transfer between the V 3+ and V 4+ layers, and is comparable to that of conventional ferroelectrics. The energy of this polar state relative to the nonpolar ground state is only 3 meV per vanadium. Under tensile strain, this energy difference can be further reduced, suggesting that the polar phase can be induced by applied electric field, yielding an antiferroelectric double-hysteresis loop. If the system does not switch back to the nonpolar state on removal of the field, a ferroelectric-type hysteresis loop could be observed. PACS numbers: 73.21.Cd, 75.25.Dk, 77.55.Px The investigation of novel mechanisms for ferroelectricity has attracted much interest in recent years, especially in the search for ferroelectrics with properties, such as ferromagnetism, that are contraindicated by the mechanism driving ferroelectricity in the prototypical perovskite titanates [1]. One approach, proposed by Khomskii [2,3] is to combine two symmetry-breaking orderings, neither of which separately lift inversion symmetry, to generate a switchable polar structure [4]. The specific orderings discussed by Khomskii are sitecentered charge ordering and bond-centered charge ordering. Ferroelectricity and multiferroelectricity induced by charge order have been proposed and reported in various magnetites, manganates, and charge transfer organic salts [2,3,5]. In some of these materials, the polarization is dominated by the electron transfer producing the charge order rather than by ionic displacements, leading to the term "electronic ferroelectricity." [6][7][8] In perovskite transition metal (TM) oxide (ABO 3 ) n (A BO 3 ) m (001) superlattices, the layered cation ordering lowers the symmetry from cubic to tetragonal and breaks up-down symmetry across BO 2 layers. Control of the TM d-orbital occupancy through choice of A cations and layer thicknesses to obtain a mixed valence leads to charge disproportionation and long-range charge ordering [9-12]. As we will discuss further below, layered charge ordering breaks the up-down symmetry across the AO and A O layers. Thus, the combination of these two symmetry-breaking orderings (TM site-centered charge ordering and layered cation ordering) can generate a switchable polar structure with polarization normal to the layers.A 1:1 superlattice composed of LaVO 3 and SrVO 3 is a promising candidate for this type of charge-order-induced ferroelectricity. The low temperature phases of orthorhombic LaVO 3 and cubic SrVO 3 are antiferromagnetic Mottinsulating and correlated metallic, respectively [9,[13][14][15]. When they f...