Stochastic quantum molecular dynamics for finite and extended systems

We present a detailed account of the technical aspects of stochastic quantum molecular dynamics, an approach introduced recently by the authors [H. Appel, M. Di Ventra, Phys. Rev. B 80 (2009) 212303] to describe coupled electron-ion dynamics in open quantum systems. As example applications of the method we consider both finite systems with and without ionic motion, as well as describe its applicability to extended systems in the limit of classical ions. The latter formulation allows the study of important phenomena such as decoherence and energy relaxation in bulk systems and surfaces in the presence of time-dependent fields.     

A ‘waterproof’ catalyst for the oxidation of secondary amines to nitrones with alkyl hydroperoxides

Catalytic oxidation of secondary amines to nitrones using alkyl hydroperoxides as primary oxidant has been demonstrated for the first time. The titanium alkoxide catalyst is protected from co-product water by the combined use of a tightly binding trialkanolamine ligand and molecular sieves. Nitrones can be obtained in high yield (up to 98%) under homogeneous, anhydrous conditions and even in the absence of solvent. The reactions are fast (2-7 h) and good selectivity can be achieved with as little as 1% catalyst.     

Stochastic time-dependent current-density-functional theory

A time-dependent current-density-functional theory for many-particle systems in interaction with arbitrary external baths is developed. We prove that, given the initial quantum state |Psi0> and the particle-bath interaction operator, two external vector potentials A(r,t) and A'(r,t) that produce the same ensemble-averaged current density, j(r,t), must necessarily coincide up to a gauge transformation. This result greatly expands the applicability of time-dependent density-functional theory to open quantum systems, and allows for first-principles calculations of many-particle time evolution beyond Hamiltonian dynamics.     

Next-to-next-to-leading-order subtraction formalism in hadron collisions and its application to Higgs-boson production at the large hadron collider

We consider higher-order QCD corrections to the production of colorless high-mass systems (lepton pairs, vector bosons, Higgs bosons, etc.) in hadron collisions. We propose a new formulation of the subtraction method to numerically compute arbitrary infrared-safe observables for this class of processes. To cancel the infrared divergences, we exploit the universal behavior of the associated transverse-momentum (qT) distributions in the small-qT region. The method is illustrated in general terms up to the next-to-next-to-leading order in QCD perturbation theory. As a first explicit application, we study Higgs-boson production through gluon fusion. Our calculation is implemented in a parton level Monte Carlo program that includes the decay of the Higgs boson into two photons. We present selected numerical results at the CERN Large Hadron Collider.     

Equivalent dissipation postulates in classical plasticity

Summary In classical plasticity dissipation postulates on cycles, such as those proposed by Drucker, Martin e Il'yushin, rule the evolution of elastic-plastic deformation processes. In this paper, within the framework of the infinitesimal theory of isotropic materials with elastic range of [7], each one of those three postulates is given an equivalent local formulation; moreover, they are shown to be all equivalent.

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Sommario In plasticitá classica l'evoluzione dei processi elasto-plastici é regolata da postulati di dissipazione su cicli quali quelli proposti da Drucker, Martin e Il'yushin. In questo lavoro, nell'ambito della teoria infinitesima dei materiali isotropi con dominio elastico proposta in [7], si fornisce una formulazione locale equivalent per ciascuno di quei tre postulati e si mostra che essi sono tutti tra loro equivalenti.

     

Chains,Necklaces and Weaving Chain‐link Grids from Self‐Assembly Reactions

Assembly of two ditopic units, a phenanthroline substituted by 4‐ethynyl pyridines at the 2‐and 9‐positions and a dimetallic paddlewheel, gives a linear chain polymer rather than a closed cyclic species, which would appear equally possible. The chain may be decorated by binding a copper‐containing macrocycle around the phenanthroline units to form a polypseudorotaxane. When two phenanthroline ligands are assembled in a first step around copper(I), the paddlewheel acceptor can link them in a second step to form a two‐dimensional interwoven grid that resembles the form of a chain‐link fence. Each copper(I) centre in this structure is chiral, and the crystal shows complete homochirality, implying selection during the assembly process.     

Direct On‐Surface Patterning of a Crystalline Laminar Covalent Organic Framework Synthesized at Room Temperature

We report herein an efficient, fast, and simple synthesis of an imine‐based covalent organic framework (COF) at room temperature (hereafter, RT‐COF‐1 ). RT‐COF‐1 shows a layered hexagonal structure exhibiting channels, is robust, and is porous to N₂ and CO₂. The room‐temperature synthesis has enabled us to fabricate and position low‐cost micro‐ and submicropatterns of RT‐COF‐1 on several surfaces, including solid SiO₂ substrates and flexible acetate paper, by using lithographically controlled wetting and conventional ink‐jet printing.     

Stabilization of Titanium Dioxide Nanoparticles at the Surface of Carbon Nanomaterials Promoted by Microwave Heating

TiO₂ is frequently combined with carbon materials, such as reduced graphene oxide (RGO), to produce composites with improved properties, for example for photocatalytic applications. It is shown that heating conditions significantly affect the interface and photocatalytic properties of TiO₂@C, and that microwave irradiation can be advantageous for the synthesis of carbon‐based materials. Composites of TiO₂ with RGO or amorphous carbon were prepared from reaction of titanium isopropoxide with benzyl alcohol. During the synthesis of the TiO₂ nanoparticles, the carbon is involved in reactions that lead to the covalent attachment of the oxide, the extent of which depends on the carbon characteristics, heating rate, and mechanism. TiO₂ is more efficiently stabilized at the surface of RGO than amorphous carbon. Rapid heating of the reaction mixture results in a stronger coupling between the nanoparticles and carbon, more uniform coatings, and smaller particles with narrower size distributions. The more efficient attachment of the oxide leads to better photocatalytic performance.