Random walk model for coordinate dependent diffusion in a force field

TL;DR

This paper introduces a lattice-based random walk model to describe coordinate-dependent diffusion under a force field, capturing equilibrium and barrier transition behaviors more accurately than traditional models.

Contribution

It develops a novel random walk framework incorporating coordinate-dependent waiting times and jump anisotropy to model diffusion in force fields.

Findings

Equilibrium distribution follows a modified Boltzmann form.

The model accurately describes barrier crossing in systems with variable diffusivity.

Modified Boltzmann distribution outperforms classical Boltzmann in these systems.

Abstract

In this paper we develop a random walk model on lattice for coordinate dependent diffusion at constant temperature in contact with a heat bath. We employ here a coordinate dependent waiting time of the random walker to make the diffusivity coordinate dependent. The presence of a confining conservative force is modeled by appropriately breaking the isotropy of the jumps of the random walker to its nearest neighbors. We show that the equilibrium is characterized by the position distribution which is of modified Boltzmann form. We also show that, in such systems with coordinate dependent diffusivity, the modified Boltzmann distribution correctly captures the transition over a potential barrier as opposed to the Boltzmann distribution.