Shu-Feng Lee¹, Che-Wun Hong^1,2

CMC-Computers, Materials & Continua, Vol.12, No.3, pp. 223-236, 2009, DOI:10.3970/cmc.2009.012.223

Abstract Solid oxides, such as ceria (CeO₂) doped with cations of lower valance, are potential electrolytes for future solid oxide fuel cells. This is due to the theoretically high ionic conductivity at low operation temperature. This paper investigates the feasibility of two potential electrolytes which are samarium-doped ceria (SDC) and gadolinium-doped ceria (GDC) to replace the traditional yttria-stablized zirconia (YSZ). Molecular simulation techniques were employed to study the influence of different dopant concentrations at different operation temperatures on the ionic conductivity from the atomistic perspective. Simulation results show that the optimized ionic conductivity occurs at 11.11mol% concentration More >

D. S. Liu¹, C. Y. Tsai¹, S. R. Lyu²

CMC-Computers, Materials & Continua, Vol.11, No.2, pp. 147-164, 2009, DOI:10.3970/cmc.2009.011.147

Abstract This study presents a novel numerical method for extracting the tempe -rature-dependent mechanical properties of the gold and aluminum thin-films. In the proposed approach, molecular dynamics (MD) simulations are performed to establish the load-displacement response of the thin substrate nanoindented at temperatures ranging from 300-900 K. A simple but effective procedure involving genetic algorithm (GA) and finite element method (FEM) is implemented to extract the material constants of the gold and aluminum substrates. The material constants are then used to construct the corresponding stress-strain curve, from which the elastic modulus, yield stress and the tangent More >

Hsien-Chie Cheng¹, Yu-Chen Hsu², Wen-Hwa Chen²

CMC-Computers, Materials & Continua, Vol.11, No.2, pp. 127-146, 2009, DOI:10.3970/cmc.2009.011.127

Abstract Due to the limitation of fabrication technologies nowadays, structural or atomistic defects are often perceived in carbon nanotubes (CNTs) during the manufacturing process. The main goal of the study aims at providing a systematic investigation of the effects of atomistic defects on the nanomechanical properties and fracture behaviors of single-walled CNTs (SWCNTs) using molecular dynamics (MD) simulation. Furthermore, the correlation between local stress distribution and fracture evolution is studied. Key parameters and factors under investigation include the number, type (namely the vacancy and Stone-Wales defects), location and distribution of defects. Results show that the nanomechanical More >

Yeau-Ren Jeng¹,Ping-Chi Tsai¹,Guo-Zhe Huang¹, I-Ling Chang¹

CMC-Computers, Materials & Continua, Vol.11, No.2, pp. 109-126, 2009, DOI:10.3970/cmc.2009.011.109

Abstract This study performs a series of Molecular Dynamics (MD) and Molecular Statics (MS) simulations to investigate the mechanical properties of single-walled carbon nanotubes (SWCNTs) under a uniaxial tensile strain. The simulations focus specifically on the effects of the nanotube helicity, the nanotube diameter and the percentage of vacancy defects on the bond length, bond angle and tensile strength of zigzag and armchair SWCNTs. In this study, a good agreement is observed between the MD and MS simulation results for the stress-strain response of the SWCNTs in both the elastic and the plastic deformation regimes. The… More >

M. Macri¹, P. Chung¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.7, No.2, pp. 77-82, 2008, DOI:10.3970/icces.2008.007.077

Abstract In this paper, we compare three interpolation functions in a discretized continuum when used in coupled dynamic atomistic-to-continuum simulations. The focus is on assessing the ability of the discrete continuum model to capture and accurately represent transient effects, namely a travelling longitudinal wave, through both the mixed atomistic-continuum interface and the non-uniform continuum mesh beyond. We specifically examine the differences among Bubnov-Galerkin, partition of unity, and moving least squares finite element methods, which generally fall under the framework of the meshless Petrov-Galerkin Finite Elements, in the continuum part of the multiscale model, where the key More >

M. Katagiri, H. Onodera¹, H. Ogawa², N. Nishikawa³

The International Conference on Computational & Experimental Engineering and Sciences, Vol.6, No.1, pp. 72-80, 2008, DOI:10.3970/icces.2008.006.072

Abstract The microscopic mechanism of Hydrogen-Induced Amorphization (HIA) in C15 Laves phases of AB$_2$ compounds is studied. Experimentally, compounds in which the AA internuclear distance is reduced and BB internuclear distance expanded compared to pure crystals show Hydrogen-Induced Amorphization which suggests that the relative atomic size is the controlling factor. We investigate the role of the size effect by static and Molecular Dynamics methods using Lennard-Jones potentials. Our simulations show that in such a compound, the bulk modulus is remarkably reduced by hydrogenation compared to the isotropic tensile load, so that elastic instability is facilitated. This More >

Arun K. Nair¹, Diana Farkas², Ronald D. Kriz¹

CMES-Computer Modeling in Engineering & Sciences, Vol.24, No.2&3, pp. 239-248, 2008, DOI:10.3970/cmes.2008.024.239

Abstract The indentation response of Ni thin films of thicknesses in the nano scale was studied using molecular dynamics simulations with embedded atom method (EAM) interatomic potentials. Simulations were performed in single crystal films in the [111] orientation with thicknesses of 7nm and 33nm. In the elastic regime, the loading curves observed start deviating from the Hertzian predictions for indentation depths greater than 2.5% of the film thickness. The observed loading curves are therefore dependent on the film thickness. The simulation results also show that the contact stress necessary to emit the first dislocation under the More >

R. Matsumoto¹, N. Miyazaki¹, M. Nakagaki²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 223-230, 2007, DOI:10.3970/icces.2007.004.223

Abstract The mechanical properties of amorphous metals and metallic glasses are remarkably changed by precipitated crystalline particles. In this paper, the effects of crystal particle size and volume fraction on the flow stress of the metallic glass are evaluated by molecular dynamics simulations. The investigated volume fraction ranges from 0% (metallic glass) to 100% (nanocrystalline metal), and the average particle diameter ranges from 1nm to 12nm. It is revealed that the dispersed particle effects on the flow stress are very small in the entire volume fraction range when the average particle diameter is smaller than 3 More >

S. Namilae¹, U. Ch,ra², A Srinivasan³, N. Ch,ra⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.3, pp. 189-202, 2007, DOI:10.3970/cmes.2007.022.189

Abstract Molecular dynamics (MD) simulations play an important predictive role in understanding the behavior of nanoscale systems. In this paper, parallel MD simulations are used to understand the mechanical behavior of interfaces in CNT based composites. We present an algorithm for parallel implementation of MD simulations of carbon nanotube (CNT) based systems using reactive bond order potentials. We then use that algorithm to model the CNT-polymer interfaces with various levels of interaction as (a) described only by long range Van Der Waals interactions (b) chemically bonded with fixed matrix and (c) chemically bonded with matrix explicitly More >

Wenzhong Tang¹, Suresh G. Advani^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.1, pp. 31-40, 2007, DOI:10.3970/cmes.2007.022.031

Abstract In this paper, non-equilibrium molecular dynamics (MD) simulations were performed to investigate water flow around a single-walled carbon nanotube. In the simulation, the nanotube was modeled as a rigid cylinder of carbon atoms. Water molecules were described with the extended simple point charge (SPC/E) model. The nanotube-water interactions were calculated with a Lennard-Jones potential between carbon-oxygen pairs. The water-water interactions comprised a Lennard-Jones potential between the oxygen-oxygen pairs and a Coulomb potential between all charge sites on interactive water molecules. It was shown that classical continuum mechanics does not hold when the drag forces on More >