Choosing Spatial Resolution in the Residence-Time Approach to Local Diffusivity
Abstract
Estimating position-dependent diffusivity with the residence-time approach (RTA) requires choosing an interval width that resolves spatial variation while probing time scales compatible with a local diffusion model. We develop a selection criterion that combines bulk diffusivity convergence with local model agreement measured by the Kullback-Leibler divergence between observed and predicted first-exit-time distributions, and assess global model agreement through independent propagator analysis against unbiased molecular dynamics. Applications to water in a fluid phospholipid bilayer and three permeants in a model skin lipid barrier show that local agreement alone does not ensure global fidelity: in the skin barrier, narrow intervals minimize exit-time mismatch but predict excessive spreading, whereas requiring bulk convergence selects wider intervals with better longer-time predictions. In propagator tests, RTA profiles at the selected interval widths outperform velocity-autocorrelation-based profiles and generally improve agreement relative to position-autocorrelation-based profiles in the skin barrier, while phospholipid-bilayer rankings depend on lag time and discrepancy metric; both autocorrelation methods use harmonically restrained simulations.
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BibTeX
@misc{domaros2026choosing,
title = {{Choosing Spatial Resolution in the Residence-Time Approach to Local Diffusivity}},
author = {Michael von Domaros and Rinto Thomas and Praveen Ranganath Prabhakar},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.29703},
eprint = {2610.29703},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.29703},
}
RIS
TY - UNPB
TI - Choosing Spatial Resolution in the Residence-Time Approach to Local Diffusivity
AU - Michael von Domaros
AU - Rinto Thomas
AU - Praveen Ranganath Prabhakar
PY - 2026
DA - 2026/10/21
PB - arXiv
DO - 10.48550/arxiv.2610.29703
UR - https://arxiv.org/abs/2610.29703
AB - Estimating position-dependent diffusivity with the residence-time approach (RTA) requires choosing an interval width that resolves spatial variation while probing time scales compatible with a local diffusion model. We develop a selection criterion that combines bulk diffusivity convergence with local model agreement measured by the Kullback-Leibler divergence between observed and predicted first-exit-time distributions, and assess global model agreement through independent propagator analysis against unbiased molecular dynamics. Applications to water in a fluid phospholipid bilayer and three permeants in a model skin lipid barrier show that local agreement alone does not ensure global fidelity: in the skin barrier, narrow intervals minimize exit-time mismatch but predict excessive spreading, whereas requiring bulk convergence selects wider intervals with better longer-time predictions. In propagator tests, RTA profiles at the selected interval widths outperform velocity-autocorrelation-based profiles and generally improve agreement relative to position-autocorrelation-based profiles in the skin barrier, while phospholipid-bilayer rankings depend on lag time and discrepancy metric; both autocorrelation methods use harmonically restrained simulations.
ER -