CMES-Vol. 3, No. 5, 2002

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Computational Nanotechnology: A Current Perspective
Deepak Srivastava¹, Satya N. Atluri²
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 531-538, 2002, DOI:10.3970/cmes.2002.003.531
Abstract The current status of the progress and developments in computational nanotechnology is briefly reviewed, from the perspective of its applications. The enabling tools and techniques of physics- and chemistry-based simulations, within a multi-scale context , are briefly reviewed . More >

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Multiscale Modeling of Laser Ablation: Applications to Nanotechnology
Leonid V. Zhigilei¹, Avinash M. Dongare¹
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 539-556, 2002, DOI:10.3970/cmes.2002.003.539
Abstract Computational modeling has a potential of making an important contribution to the advancement of laser-driven methods in nanotechnology. In this paper we discuss two computational schemes developed for simulation of laser coupling to organic materials and metals and present a multiscale model for laser ablation and cluster deposition of nanostructured materials. In the multiscale model the initial stage of laser ablation is reproduced by the classical molecular dynamics (MD) method. For organic materials, the breathing sphere model is used to simulate the primary laser excitations and the vibrational relaxation of excited molecules. For metals, the… More >

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JavaGenes: Evolving Molecular Force Field Parameters with Genetic Algorithm
Al Globus¹, Madhu Menon², Deepak Srivastava¹
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 557-574, 2002, DOI:10.3970/cmes.2002.003.557
Abstract A genetic algorithm procedure has been developed for fitting parameters for many-body interatomic force field functions. Given a physics or chemistry based analytic form for the force field function, parameters are typically chosen to fit a range of structural and physical properties given either by experiments and/or by higher accuracy tight-binding or ab-initio simulations. The method involves using both near equilibrium and far from equilibrium configurations in the fitting procedure, and is unlikely to be trapped in local minima in the complex many-dimensional parameter space. As a proof of concept, we demonstrate the procedure for… More >

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Computational Studies of Molecular Diffusion through Carbon Nanotube Based Membranes
Susan B. Sinnott¹, Zugang Mao,², Ki-Ho Lee
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 575-588, 2002, DOI:10.3970/cmes.2002.003.575
Abstract Nanofluidics is an area that has been under study for some time in zeolites and ideal nanoporous systems. Computational studies of the behavior of molecules in nanoporous structures have played an important role in understanding this phenomenon as experimental studies of molecular behavior in nanometer-scale pores are difficult to perform. In this paper computational work to study molecular motion and the separation of molecular mixtures in carbon nanotube systems is reported. The systems examined include organic molecules, such as CH₄, C₂H₆, n-C₄H₁₀, and i-C₄H₁₀, and inorganic molecules, such as CO₂. The interatomic forces in the molecular dynamics simulations More >

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1002
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Select Applications of Carbon Nanotubes: Field-Emission Devices and Electromechanical Sensors
Amitesh Maiti¹
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 589-600, 2002, DOI:10.3970/cmes.2002.003.589
Abstract Atomistic modeling and simulations are becoming increasingly important in the design of new devices at the nanoscale. In particular, theoretical modeling of carbon nanotubes have provided useful insight and guidance to many experimental efforts. To this end, we report simulation results on the electronic, structural and transport properties for two different applications of carbon nanotube-based devices: (1) effect of adsorbates on field emission; and (2) effect of mechanical deformation on the electronic transport. The reported simulations are based on First Principles Density Functional Theory (DFT), classical molecular mechanics, and tight-binding transport based on the recursive More >

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Development of a Nanoelectronic 3-D (NEMO 3-D ) Simulator for Multimillion Atom Simulations and Its Application to Alloyed Quantum Dots
Gerhard Klimeck^1,2, Fabiano Oyafuso², Timothy B. Boykin³, R. Chris Bowen², Paul von Allmen⁴
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 601-642, 2002, DOI:10.3970/cmes.2002.003.601
Abstract Material layers with a thickness of a few nanometers are common-place in today's semiconductor devices. Before long, device fabrication methods will reach a point at which the other two device dimensions are scaled down to few tens of nanometers. The total atom count in such deca-nano devices is reduced to a few million. Only a small finite number of "free'' electrons will operate such nano-scale devices due to quantized electron energies and electron charge. This work demonstrates that the simulation of electronic structure and electron transport on these length scales must not only be fundamentally… More >

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Atomic Modeling of Carbon-Based Nanostructures as a Tool for Developing New Materials and Technologies
D.W. Brenner, O.A. Shenderova, D.A. Areshkin, J.D. Schall¹, S.-J. V. Frankland²
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 643-674, 2002, DOI:10.3970/cmes.2002.003.643
Abstract The derivation of a bond-order potential energy function and a self-consistent tight-binding scheme is presented, followed by a survey of the application of these methods to calculating properties of carbon nanostructures. The modeling studies discussed include properties of functionalized and kinked carbon nanotubes, Raman shifts for hydrogen stored in nanotubes, nanotubes in a composite, properties of nanotubes in applied potential (electrical) fields, and structures and properties of nanocones, nanodiamond clusters and rods, and hybrid diamond-nanotube structures. More >

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Bonding Geometry and Bandgap Changes of Carbon Nanotubes Under Uniaxial and Torsional Strain
Liu Yang¹, Jie Han, M. P. Anantram, Richard L. Jaffe
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 675-686, 2002, DOI:10.3970/cmes.2002.003.675
Abstract Bonding geometry and bandgap of carbon nantotubes under uniaxial and torsional deformation are studied computationally for nanotubes of various chiralities and diameters. Bonding geometries are obtained with Tersoff-Brenner potential from molecular mechanics simulations. Bandgaps as function of strain are calculated from the molecular mechanics structures using one (p) and four (2s and 2p_x, 2p_y, 2p_z) orbital tight-binding models. For small strains, the bandgap results are qualitatively consistent with those predicted by the one orbital analytical model. Response of the electronic properties of nanotubes to large strains is characterized by a change in sign of d(bandgap)/d(strain). These originate More >

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