Behavior
of Two-Dimensional Hydrogen-Bonded
Networks under Shear Conditions: A
First-Principles Molecular Dynamics Study
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Abstract
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 MoS<sub>2</sub>. 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 consisting of covalently or ionically bonded components, which
can be damaged irreversibly as a result of large structural deformations