The Tribological Properties of Self-Assembled Systems Using Molecular Dynamics
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Static quantum chemical calculations and first principles molecular dynamics simulations are used to examine the behavior of two-dimensional hydrogen-bonded systems under sliding conditions, with the goal of assessing whether such systems may be useful as lubricants. The results demonstrate that these systems can be effective lubricants if the hydrogen bonds (HBs) in the system are of moderate strength, evenly distributed in the system, and restricted to reside within the layers. One system that meets these conditions was found to exhibit friction forces and friction coefficients that are comparable to layered systems consisting of sheets of atoms connected via covalent or ionic bonds, such as graphite and MoS2. The results also show that the flexibility associated with the HBs allows this system to reversibly undergo large structural deformations. This ability allowed this system to undergo a slip mechanism in which the layers buckled, which was found to reduce the slip barrier. The ability to reversibly accommodate structural changes may represent an advantage of systems comprising sheets of covalently or ionically bonded components, which can be damaged irreversibly as a result of large structural deformations.