Paper Citing NAMD - Abstract
Choi, H. J.; Kim, J. Y.; Hong, S. D.; Ha, M. Y.; Jang, J.
Molecular simulation of the nanoscale water confined between an atomic force microscope tip and a surface
MOLECULAR SIMULATION, 35:466-472, 2009
Under ambient humidity, water condenses as a nanometre meniscus between an atomic force microscope (AFM) tip and a surface, giving rise to a strong capillary force on the tip. To examine the molecular features of the meniscus, we performed an all-atom molecular dynamics simulation. By varying the tip-surface distance, we have simulated the formation, thinning and snap-off of the water meniscus. The meniscus is several nanometres wide and substantially fluctuates in its periphery when its neck is narrow. The density profile of the meniscus shows that its periphery is not sharp but has a fuzzy boundary whose thickness ranges from 0.4 to 0.9 nm. We obtained the neck radius of the meniscus and the radius of curvature of its periphery. Due to the sharp asperity of the AFM tip, these two structural parameters are comparable in size, in contrast to the case of a macroscopic tip, where the neck radius is much greater. We found that the meniscus periphery is often far from a circle in shape. With the structural parameters of the meniscus, we calculated the capillary force by using the Laplace-Kelvin equation. Our calculation reproduces the typical behaviour of the force-distance curve in the AFM experiment.
