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    Investigation of a new mean temperature-dependent potential energy function for methane and its use for the prediction of transport properties

    , Article Molecular Physics ; Volume 105, Issue 10 , 2007 , Pages 1453-1463 ; 00268976 (ISSN) Nahaly, M ; Parsafar, G. A ; Goharshadi, E. K ; Sharif University of Technology
    In this work an improved mean potential energy function for the interaction of an isolated pair of methane is obtained, from which the non-equilibrium properties of methane at zero pressure limit are calculated, accurately. The potential energy function of 21 different fixed orientations of (CH4)2 dimer has been obtained via the coupled cluster method. In order to obtain a mean potential energy function, the Boltzmann-average of the obtained potentials of the selected fixed orientations has been used. Unlike the full potential energy surface with the angle-dependent, the parameters of the mean potential are found to be temperature-dependent. The mean potential energy function is fitted well... 

    Modification of Repulsive and Attraction Branches of the Potential Models to Calculate the Equilibrium and Transport Properties of Liquids

    , M.Sc. Thesis Sharif University of Technology Razavi Majarashin, Asghar (Author) ; Parsafar, GHolamabbas (Supervisor)
    Several potential models such as Sutherland (ST) and square-well (SW) potential models are used for studying the equilibrium and transport properties. Near and above the inversion temperature these potential models fail to predict the second virial coefficient, so they are not applicable at high temperatures. ST and SW potential models have two different branches; one branch is related to the attraction forces and the other to the repulsive forces. Each branch has its own unique parameters, for example parameters of attraction branch are ε/k (the depth of the potential model) and λ (the width of the potential model). Repulsive branch has only one parameter, σ (the molecular diameter).... 

    Computation of some thermodynamic properties of nitrogen using a new intermolecular potential from molecular dynamics simulation

    , Article Chemical Physics ; Volume 358, Issue 3 , 2009 , Pages 185-195 ; 03010104 (ISSN) Kafshdar Goharshadi, E ; Abbaspour, M ; Namayandeh Jorabchi, M ; Nahali, M ; Sharif University of Technology
    A new pair-potential energy function of nitrogen has been determined via the inversion of reduced viscosity collision integrals and fitted to obtain an analytical potential form. The pair-potential reproduces the second virial coefficient, viscosity, thermal conductivity, self-diffusion coefficient, and thermal diffusion factor of nitrogen in a good accordance with experimental data over wide ranges of temperatures and densities. We have also performed the molecular dynamics simulation to obtain pressure, internal energy, heat capacity at constant volume, and self-diffusion coefficient of nitrogen at different temperatures and densities using our calculated pair-potential and some other... 

    Classification of the nonlinear dynamics in an initially curved bistable micro/nanoelectro-mechanical system resonator

    , Article Micro and Nano Letters ; Volume 10, Issue 10 , Oct , 2015 , Pages 583-588 ; 17500443 (ISSN) Tajaddodianfar, F ; Hairi Yazdi, M. R ; Nejat Pishkenari, H ; Maani Miandoab, E ; Ouakad, H.M ; Sharif University of Technology
    Institution of Engineering and Technology  2015
    The nonlinear dynamics of a bistable micro/nano-electro-mechanical system resonator composed of an arch-shaped microbeam is investigated. The initially curved microbeam is actuated through a combined DC and AC electrostatic parallel plate field. A single degree of freedom model obtained using the Galerkin's decomposition method with distributed electrostatic force is implemented in order to investigate the resonator dynamics near its primary resonance. According to the shape of the potential energy function which depends on the system parameters, the nonlinear dynamics of the system are classified into certain categories. The appearance of various nonlinear phenomena including dynamic...