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The vacancy-enhanced contact friction of graphene is mainly attributed to the vacancy-enhanced out-of-plane deformation flexibility of the graphene and the climbing of the tip out of the vacancy trap (which actually acts as a step edge). However, this mechanism does not apply for explaining the enhanced friction caused by small-sized vacancies that are unable to accommodate the tip, such as single vacancy and double vacancies, which also commonly exist in the graphene. In present study, by performing a set of classic molecular dynamic (MD) simulations, we demonstrated that the double-vacancy defect in graphene substantially enhanced the contact friction when the tip slides over it, and the pinning effect of the reconstructed lattice of the double-vacancy defect with atoms at the bottom of the tip dominated such influence. The underlying mechanism of such atomic pinning effect and the influence of the normal load, sliding direction, and the sliding velocity was unveiled by analyzing the obtained friction evolution and the atomic configuration and interaction between the tip and the graphene. We believe that the findings presented in this study complete the state-of-art understanding of the nanoscale friction behaviors of vacancy-defected graphene, which is essential for the implementation of potential control of them.
This article was published in the following journal.
Name: Langmuir : the ACS journal of surfaces and colloids
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A member of the alkali metals. It has an atomic symbol Cs, atomic number 50, and atomic weight 132.91. Cesium has many industrial applications, including the construction of atomic clocks based on its atomic vibrational frequency.
Devices containing fissionable material in sufficient quantity and so arranged as to be capable of maintaining a controlled, self-sustaining NUCLEAR FISSION chain reaction. They are also known as atomic piles, atomic reactors, fission reactors, and nuclear piles, although such names are deprecated. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
Promethium. A radioactive element of the rare earth family of metals. It has the atomic symbol Pm, atomic number 61, and atomic weight 147. It has been used in the construction of atomic batteries, in the preparation of self-luminous compounds, and as a beta-particle source for thickness gauges.
A trace element that is required in bone formation. It has the atomic symbol Sn, atomic number 50, and atomic weight 118.71.
A heavy metal trace element with the atomic symbol Cu, atomic number 29, and atomic weight 63.55.
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