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We report the production and characterization of a form of amorphous carbon films with sp/sp 2 hybridization (atomic fraction of sp hybridized species ≥ 20%) where the predominant sp bonding appears to be (=C=C=) n cumulene. Vibrational and electronic properties have been studied by in situ Raman spectroscopy and electrical conductivity measurements. Cumulenic chains are substantially stable for temperatures lower than 250 K and they influence the electrical transport properties of the sp/sp 2 carbon through a self-doping mechanism by pinning the Fermi level closer to one of the mobility gap edges. Upon heating above 250 K the cumulenic species decay to form graphitic nanodomains embedded in the sp 2 amorphous matrix thus reducing the activation energy of the material. This is the first example of a pure carbon system where the sp hybridization influences bulk properties. Cumulenes are expected to tend to a metallic behavior, characterized by the homogeneous distribution of the π orbitals, as their length increases, while polyynes are expected to be semiconducing even for infinitely long chains, due to bond length alternation opening an energy gap at the edge of the Brilluoin zone [6,7].Sp chains can be stabilized by isolation in rare gas or inorganic matrices [8,5] or terminating the chain ends with suitable functional groups [6,9]. Calculations on infinite carbon chains indicate that polyynes are energetically more stable than cumulenes due to Peierls distortion [10], however for finite length chains the gain in energy is too low to be significant even a T = 0 K [11].Furthermore it has been shown that the electronic configuration of the chains is determined, regardless their length, by the group termination of the chain [6]. A conspicuous amount of experimental and theoretical results are available on the electronic structure and vibrational properties of isolated polyynes [12][13][14], whereas almost no experimental characterizations can be found on cumulenes.The possibility of stabilizing sp chains in cluster-assembled nanostructured carbon films Here we report on the production and characterization of amorphous sp/sp 2 carbon films where the dominant sp species are cumulenes. This is obtained by supersonic cluster beam deposition on a substrate kept at a temperature of 150 K. We show that cumulenes are stable up to a temperature of roughly 210 K and that they influence the electrical transport properties of the films acting as metallic doping species. By rising the film temperature to 325 K cumulenes undergo a reorganization inducing the formation of nanometric graphitic islands in the amorphous sp 2 matrix, while the amount of polyynes remains substantially constant in the investigated temperature range.Cluster-assembled films were grown in ultra high vacuum (~ 10 -9 mbar) by depositing on glass substrates a supersonic beam of carbon clusters produced by a pulsed microplasma cluster source as described in detail in refs. [19,20]; two parallel gold contacts were previously evaporated on the substrat...

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The growth process of metallofullerene was studied by the use of the molecular dynamics method. Based on density functional theory (DFT) calculations of various forms of small clusters MCn and Mn (M = La, Sc, Ni), multi-body classical potential functions for M-C and M-M interactions were constructed with the Morse term and the Coulomb term as functions of the coordinate number of a metal atom. The clustering process, starting from 500 isolated carbon atoms and 5 metal atoms, was simulated under a controlled temperature condition, Tc = 3000 K. When La atoms were applied, the stable open-cap structure surrounding the La atom resulted in the lanthanum-containing caged cluster. For the Sc-C system, the host carbon clusters were not affected as much as they were in the La-C case, because of the weaker Coulomb interaction. The precursor Sc atom was encapsulated in the host cage at the final stage of the growth process. For the Ni-C system, the precursor clusters were similar to those in Sc-C system, although the Ni atom finally stayed on the face of a large ring of the caged structure. PACS. 36.40.-c Atomic and molecular clusters -31.15.Qg Molecular dynamics and other numerical methods a Corresponding

Molecular dynamics simulations of single water, water-methanol, or water-IPA (isopropyl-alcohol) mixture droplets on a solid surface were performed with various mixture ratios. An increase in alcohol fraction generally gave an increase in droplet wettability. Both methanol and IPA molecules showed a strong preference to gather at various interfaces, with methanol molecules also showing a tendency to diffuse into the droplet bulk. Specific interfacial tensions were investigated using quasi-one-dimensional simulation systems, and liquid-vapor and solid-liquid interfacial tensions were found to decrease greatly due to the presence of interfacial alcohol, while solid-vapor interfacial tensions were proved to have little influence on wettability. Young's relation was found to hold quantitatively well for both water-methanol and water-IPA droplets. The validity of using Bakker's equation on solid-liquid interfaces was also investigated, and it was shown that for tightly spaced crystal surfaces, the introduced uncertainly is small.