José A Vergés

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We present first-principles calculations of phase coherent electron transport in a carbon nanotube (CNT) with realistic contacts. We focus on the zero-bias response of open metallic CNT's considering two archetypal contact geometries (end and side) and three commonly used metals as electrodes (Al, Au, and Ti). Our ab initio electrical transport calculations(More)
J. A. Vergés Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cient́ıficas, Cantoblanco, E-28049 Madrid, Spain (February 1, 2008) Kubo formula is used to get the d.c conductance of a statistical ensemble of two-dimensional clusters of the square lattice in the presence of standard diagonal disorder, a uniform magnetic field(More)
V. A. Ranea, A. Michaelides, R. Ramı́rez, J. A. Vergés, P. L. de Andres, and D. A. King Instituto de Ciencia de Materiales, Consejo Superior de Investigaciones Cientificas, Cantoblanco, E-28049 Madrid, Spain Instituto de Investigaciones Fisicoquı́micas Teóricas y Aplicadas CONICET,UNLP,CICPBA, Suc. 4, Casilla de Correo 16 (1900) La Plata, Argentina(More)
Based on the results of density functional theory calculations, a novel mechanism for the diffusion of water dimers on metal surfaces is proposed, which relies on the ability of H bonds to rearrange through quantum tunneling. The mechanism involves quasifree rotation of the dimer and exchange of H-bond donor and acceptor molecules. At appropriate(More)
The antiferromagnetic transition of the two dimensional Hubbard model is analyzed by comparing the available exact, numerical and mean field results. It is argued that all data is compatible with the opening of a mean field gap in a Fermi liquid of spin polarons, the so called Slater type of transition. In particular, this hypothesis explains the unusual(More)
The herringbone pattern is a pervasive structural motive found in most molecular crystals involving aromatic compounds. A plot of the experimental sublimation enthalpies of members of increasing size of the acene, phenacene and p-phenyl families versus the number of carbons uncovers a linear relationship between the two magnitudes, suggesting a major role(More)
We present a single-orbital double-exchange model, coupled with cooperative phonons (the so called breathing modes of the oxygen octahedra in manganites). The model is studied with Monte Carlo simulations. For a finite range of doping and coupling constants, a first-order metal-insulator phase transition is found, which coincides with the(More)
Model Hamiltonians have been, and still are, a valuable tool for investigating the electronic structure of systems for which mean field theories work poorly. This review will concentrate on the application of Pariser-Parr-Pople (PPP) and Hubbard Hamiltonians to investigate some relevant properties of polycyclic aromatic hydrocarbons (PAH) and graphene. When(More)