Surface stress
Properties of material at the free surface can be very different from those of the inside due to the confinement of electrons. The effect of the free surface at nanoscale becomes significant because the surface-to-volume ratio is large. I have focused on surface stress and its effect on the thermal and mechanical properties of nanoscale materials. My studies show that tensile surface stress, which causes compressive stress inside a material, is one of the main reasons for unique properties including a negative Poisson's ratio in metal nano-plates and nanowire and a negative coefficient of thermal expansion in nano-wires.
The compressive induced by tensile surface stress inside a nano-wire.
D. T. Ho, H. S. Park, S.-Y. Kwon, and S. Y. Kim, Negative thermal expansion of ultra-thin metal nanowires: A Computational Study, Nano Letters 17, 5113-5118 (2017). [link]
D. T. Ho, S.-Y. Kwon and S. Y. Kim. Metal [100] nanowires with negative Poisson’s ratio, Nature Scientific Reports 6, 27560 (2016). [link]
D. T. Ho, H. K. Kim, S.-Y. Kwon and S. Y. Kim. Auxeticity of face-centered cubic metal (001) nanoplates, Physica Status Solidi B 252, 1492 (2015). [link]
D. T. Ho, S.-D. Park, H. S. Lee, S.-Y. Kwon, and S. Y. Kim. Strong correlation between surface stress and mechanical strain in Cu, Ag, and Au, Europhysics Letters 106, 36001 (2014). [link]
D. T. Ho, S.-D. Park, S.-Y. Kwon, K.-B. Park and S. Y. Kim, Negative Poisson’s ratio in metal nanoplates, Nature Communication 5, 3255 (2014). [link]
