S. Di Napoli

Correlated dynamics of water and amphiphilic molecules in thin Newton black films

The dynamical properties of amphiphilics in Newton black films, as well as those of the water confined between the two charged hydrophilic surfaces, have been calculated via a series of molecular dynamic calculations in several films with different water contents. A charged semiflexible amphiphilic model and the TIP5P model of water are used in our simulations [Z. Gamba, J. Chem. Phys. 129, 164901 (2008)]. We calculate the diffusion coefficients, reorientational dynamics, and the atomic density profile of water molecules as a function of the number of water molecules per amphiphilic (n(w)). We also analyze the reorientational motion of the amphiphilics and determine a strong correlation between the dynamics of water molecules and the translational and reorientational dynamics of the amphiphilics, as well as a correlation between the reorientational dynamics of the amphiphilics belonging to the upper and lower halves of the studied thin films.

Modeling impurity-assisted chain creation in noble-metal break junctions

In this work we present the generalization of the model for chain formation in break junctions, introduced by Thiess et al (2008 Nano Lett. 8 2144), to zigzag transition-metal chains with s and p impurities. We apply this extended model to study the producibility trends for noble-metal chains with impurities, often present in break junction experiments, namely, Cu, Ag and Au chains with H, C, O and N adatoms. Providing the material-specific parameters for our model from systematic full-potential linearized augmented plane-wave first-principles calculations, we find that the presence of such impurities crucially affects the binding properties of the noble-metal chains. We reveal that both the impurity-induced bond strengthening and the formation of zigzag bonds can lead to a significantly enhanced probability for chain formation in break junctions.

Non-Fermi-liquid behavior in nonequilibrium transport through Co-doped Au chains connected to fourfold symmetric leads

Fil: Di Napoli, Solange Mariel. Comision Nacional de Energia Atomica. Centro Atomico Constituyentes. Departamento de Fisica; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Kondo behavior and conductance through 3d impurities in gold chains doped with oxygen

Combining ab initio calculations and effective models derived from them, we discuss the electronic structure of oxygen doped gold chains when one Au atom is replaced by any transition-metal atom of the 3d series. The effect of O doping is to bring extended Au 5dxz and 5dyz states to the Fermi level, which together with the Au states of zero angular momentum projection leads to three possible channels for the screening of the magnetism of the impurity. For most 3d impurities the expected physics is similar to that of the underscreened Kondo model, with singular Fermi liquid behavior. For Fe and Co under a tetragonal crystal field introduced by leads, the system might display a non-Fermi liquid behavior. Ni and Cu impurities are described by a S = 1 two channel Kondo model and an SU(4) impurity Anderson model in the intermediate valence regime, respectively. In both cases, the system is a Fermi liquid, but the conductance shows some observable differences with the ordinary SU(2) Anderson model.

Kondo physics in a Ni impurity embedded in O-doped Au chains

By means of ab initio calculations we study the effect of O-doping of Au chains containing a nanocontact represented by a Ni atom as a magnetic impurity. In contrast to pure Au chains, we find that with a minimun O-doping the

Unusual Kondo Physics in a Co Impurity Atom Embedded in Noble-Metal Chains

5d_{xz,yz}

Effect of magnetism and light sp-dopants on chain creation in Ir and Pt break junctions

states of Au are pushed up, crossing the Fermi level. We also find that for certain O configurations, the Ni atom has two holes in the degenerate

Appearance of inverse giant magnetoresistance in noncollinear magnetic systems

3d_{xz,yz}

Magnetic order in RMn2Ge2 (R=Y,Ca) compounds and their solid solutions with LaMn2Ge2

orbitals, forming a spin

Magnetic structure and transport properties of noncollinear LaMn2X2 (X=Ge, Si) systems

S=1