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 >

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 >

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 >

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 >

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 >

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 >

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 >

Yansong Wang¹, Q. Jane Wang¹, Chih Lin²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.4, pp. 517-530, 2002, DOI:10.3970/cmes.2002.003.517

Abstract Many mechanisms, such as computer hard drives, gear trains, and machine tool spindle systems, operate under both axial and radial loads, which should be respectively supported by a thrust and a journal bearing. By utilizing the end face of the shaft of a journal bearing as a thrust bearing, a coupled journal-thrust bearing system can be formed. This paper presents a mixed lubrication model developed to investigate the lubrication of this coupled bearing system. A conformal-mapping method is used in the model formulation to facilitate a universal flow description. The performance of typical coupled bearing More >

Fanghui Shi, Rohit Paranjpe¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.4, pp. 507-516, 2002, DOI:10.3970/cmes.2002.003.507

Abstract This paper describes an implicit finite element cavitation algorithm. The cavitation problem is formulated using the complementarity form. By using the complementarity formulation, the fluid pressure in the non-cavitation region and the density of the air/fluid mixture in the cavitation region are solved simultaneously. The stream-wise biasing approach is used to produce oscillation-free solution at the fluid film reformation boundary. Implicit scheme is implemented to yield stability for time marching. The algorithm is compared with the established finite volume methods, and the robustness and the correctness of the algorithm is verified. More >

P. Sainsot¹, C. Jacq², D. Nélias¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.4, pp. 497-506, 2002, DOI:10.3970/cmes.2002.003.497

Abstract Pressure distributions calculated in the simulation of rough contacts show high values and induce high stresses just beneath the surface. These stresses often exceed the yield strength of the material, therefore, a purely elastic contact model is restrictive. Plastic flow occurs and modifies the surface shape and consequently modifies the surface pressure.
This paper presents a numerical model for 3D-elastoplastic rough contact. It allows the determination of real pressure and permanent surface displacement (flattening of asperities) as well as residual stresses and plastic strains useful in fatigue analysis. The material is assumed to follow the More >