Asymmetrical free diffusion with orientation-dependence of molecules in finite timescales

TL;DR

This study reveals that nanoscale molecules with asymmetric structures exhibit orientation-dependent diffusion within finite timescales, highlighting the importance of orientation effects on nanoscale diffusion behavior.

Contribution

The paper demonstrates, through molecular dynamics simulations, that asymmetric molecules show orientation-dependent diffusion within picoseconds to nanoseconds, extending Einstein's diffusion theory to the nanoscale.

Findings

Approximately 10% more likelihood of moving along initial orientation in 100 ps

Diffusion distances reach about 1 nm within this timescale

Orientation-dependent damping force influences nanoscale diffusion

Abstract

Using molecular dynamics simulations, we show that free diffusion of a nanoscale particle (molecule) with asymmetric structure critically depends on the orientation in a finite timescale of picoseconds to nanoseconds. In a timescale of ~100 ps, there are ~10% more possibilities for the particle moving along the initial orientation than moving opposite to the orientation; and the diffusion distances of the particle reach ~1 nm. We find that the key to this observation is the orientation-dependence of the damping force to the moving of the nanoscale particle and a finite time is required to regulate the particle orientation. This finding extends the work of Einstein to nano-world beyond random Brownian motion, thus will have a critical role in the understanding of the nanoscale world.