Molecular Dynamics Simulation of Nanoforces between Substrates Mediated by Liquid Bridges: Controlling Separation and Force Fluctuations

Abstract

Molecular dynamics simulations allow determination of the force between a tip and a sample mediated by a fluid or a nanoscale capillary bridge at any separation distance in approach–retract cycles. However, without further consideration, the procedure leads to force–distance curves without control of tip-to-sample distance and tip oscillations. Here we show that the solution of a macroscopic model describing the dynamics of the tip–sample interaction can precisely guide the choice of optimum parameters, for instance, tip elastic constant and approach speed, for controlled simulations. The method is applied to the interaction between two substrates in two cases of intervening fluid: a water bridge and a Lennard-Jones bridge. The method can be very useful in the determination of force–distance curves in more complex systems.