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Author

Kwon, Soon-Yong
Frontier, Innovative Nanomaterials & Devices (FIND) Lab
Research Interests
  • Semiconductor Epitaxy, thin film technology & surface/ interface Science

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Negative Thermal Expansion of Ultrathin Metal Nanowires: A Computational Study

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Title
Negative Thermal Expansion of Ultrathin Metal Nanowires: A Computational Study
Author
Ho, Duc TamKwon, Soon-YongPark, Harold S.Kim, Sung Youb
Keywords
elastic softening; metal nanowire; molecular dynamics; Negative thermal expansion; surface stress
Issue Date
201708
Publisher
AMER CHEMICAL SOC
Citation
NANO LETTERS, v.17, no.8, pp.5113 - 5118
Abstract
Most materials expand upon heating because the coefficient of thermal expansion (CTE), the fundamental property of materials characterizing the mechanical response of the materials to heating, is positive. There have been some reports of materials that exhibit negative thermal expansion (NTE), but most of these have been in complex alloys, where NTE originates from the transverse vibrations of the materials. Here, we show using molecular dynamics simulations that some single crystal monatomic FCC metal nanowires can exhibit NTE along the length direction due to a novel thermomechanical coupling. We develop an analytic model for the CTE in nanowires that is a function of the surface stress, elastic modulus, and nanowire size. The model suggests that the CTE of nanowires can be reduced due to elastic softening of the materials and also due to surface stress. For the nanowires, the model predicts that the CTE reduction can lead to NTE if the nanowire Young’s modulus is sufficiently reduced while the nanowire surface stress remains sufficiently large, which is in excellent agreement with the molecular dynamics simulation results. Overall, we find a “smaller is smaller” trend for the CTE of nanowires, leading to this unexpected, surface-stress-driven mechanism for NTE in nanoscale materials.
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DOI
http://dx.doi.org/10.1021/acs.nanolett.7b02468
ISSN
1530-6984
Appears in Collections:
MNE_Journal Papers
MSE_Journal Papers

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