The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform

Weihong Qi - One of the best experts on this subject based on the ideXlab platform.

Qing Jiang - One of the best experts on this subject based on the ideXlab platform.

  • Cohesive Energy resolved bandgap of nanoscale graphene derivatives
    ChemPhysChem, 2014
    Co-Authors: Qing Jiang
    Abstract:

    With a size-dependent Cohesive Energy formula for two-dimensional coordinated materials, the bandgap variation in quantum dots and nanoribbons of graphene derivatives, such as graphane, fluorographene and graphene oxides, is investigated. The bandgap is found to increase substantially as the diameter or width of the nano-sized material decreases. The bandgap variation is attributed to the change in Cohesive Energy of edge carbon atoms, and is associated with the physicochemical nature and degree of edge saturation. These predictions agree with previously reported computer simulation results, and have potential application in wide-band optics and optoelectronics.

  • Cohesive‐Energy‐Resolved Bandgap of Nanoscale Graphene Derivatives
    ChemPhysChem, 2014
    Co-Authors: Qing Jiang
    Abstract:

    With a size-dependent Cohesive Energy formula for two-dimensional coordinated materials, the bandgap variation in quantum dots and nanoribbons of graphene derivatives, such as graphane, fluorographene and graphene oxides, is investigated. The bandgap is found to increase substantially as the diameter or width of the nano-sized material decreases. The bandgap variation is attributed to the change in Cohesive Energy of edge carbon atoms, and is associated with the physicochemical nature and degree of edge saturation. These predictions agree with previously reported computer simulation results, and have potential application in wide-band optics and optoelectronics.

  • Cohesive Energy of clusters referenced by wulff construction
    Journal of Physical Chemistry C, 2009
    Co-Authors: Hai Li, Ming Zhao, Qing Jiang
    Abstract:

    The geometrical and energetic characteristics of Wulff construction are expressed by variants δ, Ba/Bt, and Ec(N)/Eb0 in an N atom system, where δ = Ns/N is the surface/volume ratio with Ns being the surface atom number, Ba is the rest bond number, Bt denotes the total bond number without broken bonds, and Ec(N) and Eb0 are the Cohesive Energy values in an N atom system and in bulk. It is found that these functions of Wulff construction correspond to that of several standard clusters. Thus, Wulff construction as a first-order approximation could estimate the shape and Energy of clusters without any structural consideration.

  • size and structural dependence of Cohesive Energy in cu
    Journal of Physical Chemistry C, 2008
    Co-Authors: W T Zheng, Qing Jiang
    Abstract:

    The Cohesive Energy of Cu clusters (Ec) containing different numbers of atoms (n) in the metastable structures of pyramids, nanotubes, nanorods, films, and icosahedrons is determined using ab initi...

  • Cohesive Energy and surface Energy of fcc metallic nanocrystals
    2008 2nd IEEE International Nanoelectronics Conference, 2008
    Co-Authors: Qing Jiang
    Abstract:

    The model for the surface Energy of fcc metallic nanoparticles is developed based on the model for size-dependent Cohesive Energy and surface bond deficit consideration for the nanoparticles. Firstly, through the study the surface/volume ratio and surface CN(coordinate number) of the Wulff structure, the Cohesive Energy of interior atoms is determined. It is found that as same as the Cohesive Energy for the whole particles, the Cohesive Energy of interior atoms also decrease with the decreasing size. Considering the weakness of the Cohesive Energy and the increase of the surface bonds defect, size dependent surface Energy of fec metallic nanoparticles is determined. It is found that the surface Energy have reduction firstly and turn back to increase when the size approach to critical size of particles. The reduction of surface Energy is mainly due to the decrease of Cohesive Energy. The following increase of surface Energy is due to the decrease of surface CN. Our prediction for the surface Energy is agreed with the simulation results for metallic nanoparticles.

A. Safaei - One of the best experts on this subject based on the ideXlab platform.

  • Cohesive Energy and physical properties of nanocrystals
    Philosophical Magazine, 2011
    Co-Authors: A. Safaei
    Abstract:

    Recently, a lattice-type-sensitive model, free of any adjustable parameter, for the size dependence of the Cohesive Energy of nanocrystals (nanodisks, -films, -wires and -particles) has been developed, taking into account the effects of the averaged structural and energetic properties of their surface and volume. These effects are related to the first- and second-nearest-neighbor atomic interactions. Now, considering the intimate relation between Cohesive Energy and other physical properties of materials, the recently obtained formula for the Cohesive Energy of nanocrystals has been applied to the cases of melting point (In, Bi, Si and Ag), evaporation temperature (Ag and Au), vacancy formation Energy (Au), diffusion activation Energy (Au), surface Energy (Au, Al and Na), liquid–vapor interfacial Energy (Al and Na), Curie temperature (Pb), Debye temperature (Au and Fe) and band gap Energy (Si) of nanocrystals. In general, good agreement between the present model and the data has been obtained. Moreover, t...

  • shape structural and energetic effects on the Cohesive Energy and melting point of nanocrystals
    Journal of Physical Chemistry C, 2010
    Co-Authors: A. Safaei
    Abstract:

    A nonlinear, lattice type-sensitive model, free of any adjustable parameter, has been developed to account for the shape and size dependency of the Cohesive Energy of free-standing nanocrystals (nanoparticles, -wires, and -films). In this model, the effects of the averaged structural and energetic properties of the surface and the volume of nanocrystals along with the first and second nearest-neighbor atomic interactions have been taken into consideration and gathered in a new parameter named as the surface-to-volume Energy contribution ratio. This model has been compared to the experimental data of the Cohesive Energy of W and Mo nanoparticles, and the melting points of Au, Pb, Al, and Sn nanoparticles and Pb and In nanofilms. Moreover, the model has been corrected to account for the effect of substrate on the melting point of substrate-supported Sn nanodisks. It has been found that the present model has generally a good agreement with those experimental data measured by different techniques under differ...

  • modeling the Cohesive Energy and melting point of nanoparticles by their average coordination number
    Solid State Communications, 2008
    Co-Authors: Attarian M Shandiz, A. Safaei, S Sanjabi, Z H Barber
    Abstract:

    We present a relation between the average coordination number and the Cohesive Energy for nanoparticles that shows that the ratio of nanoparticles Cohesive Energy to the bulk value is equal to the ratio of the nanoparticles average coordination number to that of the bulk. We consider the effect of lattice and surface packing factors on the average coordination numbers of the atoms in the nanoparticle. The melting temperature of nanoparticles has been calculated from the obtained relation for Cohesive Energy, and predictions for the Cohesive Energy and melting temperature of the nanoparticles have been compared with other theoretical models and available experimental data and the results of molecular dynamics simulations.

Karl F Freed - One of the best experts on this subject based on the ideXlab platform.

  • influence of Cohesive Energy on the thermodynamic properties of a model glass forming polymer melt
    Macromolecules, 2016
    Co-Authors: Wensheng Xu, Jack F Douglas, Karl F Freed
    Abstract:

    Monomer chemical structure and architecture represent the most important characteristics of polymers that affect basic molecular parameters (such as the microscopic Cohesive Energy parameter ϵ and chain persistence length) and that correspondingly govern the bulk physical properties of polymer materials. Here, we focus on elucidating how the microscopic parameter ϵ influences the bulk thermodynamic properties of polymer melts by using molecular dynamics simulations for a standard coarse-grained bead–spring model of unentangled polymer melts under both constant volume and constant pressure conditions. Basic dimensionless thermodynamic properties, such as the Cohesive Energy density, thermal expansion coefficient, isothermal compressibility, and surface tension, are found to be universal functions of the temperature scaled by ϵ, and thermodynamic signatures for the onset and end of glass formation are identified based on observable features from the static structure factor. We also find that general trends ...

  • influence of Cohesive Energy and chain stiffness on polymer glass formation
    Macromolecules, 2014
    Co-Authors: Wensheng Xu, Karl F Freed
    Abstract:

    The generalized entropy theory is applied to assess the joint influence of the microscopic Cohesive Energy and chain stiffness on glass formation in polymer melts using a minimal model containing a single bending Energy and a single (monomer averaged) nearest neighbor van der Waals Energy. The analysis focuses on the combined impact of the microscopic Cohesive Energy and chain stiffness on the magnitudes of the isobaric fragility parameter mP and the glass transition temperature Tg. The computations imply that polymers with rigid structures and weak nearest neighbor interactions are the most fragile, while Tg becomes larger when the chains are stiffer and/or nearest neighbor interactions are stronger. Two simple fitting formulas summarize the computations describing the dependence of mP and Tg on the microscopic Cohesive and bending energies. The consideration of the combined influence of the microscopic Cohesive and bending energies leads to the identification of some important design concepts, such as i...

Junhua Zhao - One of the best experts on this subject based on the ideXlab platform.

  • continuum modeling of the Cohesive Energy for the interfaces between films spheres coats and substrates
    Computational Materials Science, 2015
    Co-Authors: Junhua Zhao, Lixin Lu, Zhiliang Zhang, Timon Rabczuk
    Abstract:

    Abstract Explicit solutions of the Cohesive Energy for the interfaces between film/coat, sphere/coat, sphere/matrix and sphere/substrate are obtained by continuum modeling of the van der Waals interaction between them. The analytical results show that the Cohesive Energy strongly depends on their size and spacing. For a given film thickness and sphere radius, the Cohesive strength increases with increasing coat thickness and then tends to a constant when the coat thickness is up to a critical value. The Cohesive strength for the interface between sphere/matrix keeps a constant when the sphere radius is up to a critical value. Checking against full atom molecular mechanics calculations show that the continuum solution has high accuracy. The established analytical solutions should be of great help for understanding the interactions between the nanostructures and substrates, biomaterials, designing nanocomposites and nanoelectromechanical systems.

  • a theoretical analysis of Cohesive Energy between carbon nanotubes graphene and substrates
    Carbon, 2013
    Co-Authors: Junhua Zhao, Jinwu Jiang, Timon Rabczuk
    Abstract:

    Explicit solutions for the Cohesive Energy between carbon nanotubes, graphene and substrates are obtained through continuum modeling of the van der Waals interaction between them. The dependence of the Cohesive Energy on their size, spacing and crossing angles is analyzed. Checking against full atom molecular dynamics calculations and available experimental results shows that the continuum solution has high accuracy. The equilibrium distances between the nanotubes, graphene and substrates with minimum Cohesive Energy are also provided explicitly. The obtained analytical solution should be of great help for understanding the interaction between the nanostructures and substrates, and designing composites and nanoelectromechanical systems.