Molecular transport through a bottleneck driven by external force

The transport phenomena of Lennard-Jones molecules through a structural bottleneck driven by an external force are investigated by molecular dynamics simulations. We observe two distinct molecular flow regimes distinguished by a critical external force Fc and find scaling behaviors between external forces and flow rates. Below the threshold Fc, molecules are essentially stuck in the bottleneck due to the attractive interaction between the molecules, while above Fc, molecules can smoothly move in the pipe. A critical flow rate qc corresponding to Fc satisfies a simple relationship with angles and the value of qc can be estimated by a simple argument. We further clarify the role of the temperature dependence in the molecular flows through the bottleneck.