L. Dai¹, V.B.C. Tan^1,2, C.H. Sow^1,3, C.T. Lim^1,2,4, W.C.D. Cheong⁵

The International Conference on Computational & Experimental Engineering and Sciences, Vol.9, No.3, pp. 151-162, 2009, DOI:10.3970/icces.2009.009.151

Abstract The mechanisms governing the tensile response of TiO₂ nanowires were studied by molecular dynamics simulations. The free side surfaces of the nanowires were found to be undulating because atoms near the free surface were relaxed into a disordered state during thermodynamic equilibration. For wires below a threshold diameter of around 10 Å, this free surface effect extends throughout the entire wire, resulting in a complete lack of ordered structure. For thick nanowires, the core of the wire retains a crystalline structure. The thicker the wire, the larger the crystalline core and the more dominant is its More >

Chih-Wei Hsieh¹, Chien-Li Wu¹, Cheng-Kuo Sung^1,2

The International Conference on Computational & Experimental Engineering and Sciences, Vol.13, No.2, pp. 33-34, 2009, DOI:10.3970/icces.2009.013.033

Abstract Molecular dynamics (MD) simulation has been demonstrated as a promising method to analyze formation and friction mechanisms of the nanoimprint process. Especially, it provides a useful tool for investigating critical issues that are generally difficult to be examined by the experiment because of cross talks among influential factors or attainability of direct measurement. This study utilized the friction mechanism to explore the factors that would affect the quality of mold replication in the direct nanoimprint. Those factors included mechanical properties of thin films, interaction force between mold and thin-film materials, and surface roughness of the… More >

N. J. Lee, C.R. Welch¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.13, No.1, pp. 11-12, 2009, DOI:10.3970/icces.2009.013.011

Abstract Carbon nanotubes have significant potential as the basis for super infrastructure material. The shear modulus of carbon nanotube ensembles is relatively low, comparable to graphite, as the carbon nanotubes interact via weak van der Waals forces. Unmodified, their intermolecular interactions are insufficient to take full advantage of the extraordinarily high strengths predicted for carbon nanotube-based fibers. Thus, a key to their use in high-strength materials is developing strong bonds between these molecules. In this study, we examine the potential development of covalent bonds between carbon nanotube pairs cross-bonded by proton bombardment using molecular dynamics simulation. More >

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

The International Conference on Computational & Experimental Engineering and Sciences, Vol.12, No.2, pp. 73-74, 2009, DOI:10.3970/icces.2009.012.073

Abstract Due to the limitation of fabrication technologies nowadays, initial defects in carbon nanotubes (CNTs) are inevitably perceived particularly during the manufacturing process or chemical treatment. The investigation of the effects of initial defects existing in CNTs on their mechanical properties and fracture behaviors becomes essential for their potentiality in engineering applications.
In this study, the defect effects, including number in percentage, type, and location, are explored using the molecular dynamics (MD) simulation with Tersoff Brenner potential. Results show that the mechanical properties, such as the elastic modulus, failure strength and strain, are strongly affected by the… More >

Hsien-Chie Cheng¹, Chun-Hung Wu², Yang-Lun Liu², Wen-Hwa Chen²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.11, No.3, pp. 65-66, 2009, DOI:10.3970/icces.2009.011.065

Abstract This study attempts to explore the thermal effect on the vibrational behaviors of single-walled carbon nanotube (SWCNT) using both a constant temperature molecular dynamics (MD) simulation that incorporates a Nosé-Hoover thermostat and a modified molecular structure mechanics (MMSM) model. The MD simulation is combined with a Nosé-Hoover thermostat, which controls the temperature of the system by an additional thermal reservoir. On the other hand, the MMSM model adopts equivalent beam elements and spring elements to simulate the bonding and non-bonding interactions between atoms, respectively, where the effect of temperatures can be also taken into account… More >

Tei-Chen Chen^1,2, Heng-Chieh Wang¹, Shu-Fan Wu¹, Yen-Hung Lin¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.9, No.4, pp. 247-262, 2009, DOI:10.3970/icces.2009.009.247

Abstract Mechanical properties of materials in the micro- and nano-meter scale have been successfully obtained by using the indentation technique. Up to now, large-scale atomistic models to simulate the experimental condition, however, still remain computationally demanding. In this article, a simple and accurate method is proposed to derive the intermolecular potential functions of coarse-grained molecular dynamics (CGMD) suitable for various single crystalline materials. This CGMD technique is then provided to simulate nano-indentation process to verify its accuracy and reliability. Simulation results evaluated by CGMD approach are obtained and compared to those predicted by MD. It is More >

Youngmin Lee, Jae Shin Park, Seyoung Im

The International Conference on Computational & Experimental Engineering and Sciences, Vol.10, No.2, pp. 51-52, 2009, DOI:10.3970/icces.2009.010.051

Abstract We study energetics and mobility of dislocations in silicon crystal in atomistic scale. The electronic structure of silicon affects its dynamics, so that it is analyzed with tight-binding method for high accuracy, emerged as a useful method for studying structural and dynamical properties of covalent systems. The tight biding potential used for silicon crystalline is the one of GSP known as a transferable potential. Due to the nature of rare events, the analysis is executed by action-derived molecular dynamics (ADMD) calculations. The changes of the system energy due to dislocation glide are explored with a More >

Chun-Lang Yeh¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.9, No.2, pp. 81-94, 2009, DOI:10.3970/icces.2009.009.081

Abstract In this study, the vaporization process of a nanojet is investigated by molecular dynamics simulation. Liquid argon nanojet made of 44000 Lennard-Jones molecules is investigated under various simulation parameters to examine their influence on the nanojet vaporization process. Snapshots of the molecules, evolution of the density field, and evolution of the intermolecular force are analyzed. The present simulation results can provide insight into the fundamental mechanism of the atomization process and will be helpful for the design of nanojet devices such as nano-printer or nano-sprayer. More >

Chun-Lang Yeh ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.3, pp. 253-284, 2009, DOI:10.3970/cmes.2009.050.253

Abstract This paper investigates the instability of a liquid thread by molecular dynamics (MD) simulation. The influences of liquid thread radius, fundamental cell length, and temperature are discussed. Snapshots of molecules, number of liquid particles formed, and density field are analyzed. Two linear stability criteria, namely Rayleigh's stability criterion and Kim's stability criterion, are accessed for their validity in molecular scale. It is found that a liquid thread is more unstable and produces more liquid particles in the fundamental cell when it is thinner or at a higher temperature. In addition, a liquid thread with a More >

Tai-Ming Chang¹, Chien-Chou Weng¹, Mei-Jiau Huang^1,2, Chun-KaiLiu², Chih-Kuang Yu²

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.1, pp. 47-66, 2009, DOI:10.3970/cmes.2009.050.047

Abstract We employ the non-equilibrium molecular dynamics (NEMD) simulation to calculate the in-plane thermal conductivity of silicon thin films of thickness 2.2nm and 11nm. To eliminate the finite-size effect, samples of various lengths are simulated and an extrapolation technique is applied. To perform the quantum correction which is necessary as the MD simulation temperature is lower than Debye temperature, the confined phonon spectra are obtained in advance via the EMD simulations. The investigation shows the thermal conductivities corrected based on the bulk and thin-film phonon densities of states are very close and they agree excellently with More >