Microstructural geometry revealed by NMR lineshape analysis

We introduce a technique for extracting microstructural geometry from NMR lineshape analysis in porous materials at angstrom-scale resolution with the use of weak magnetic field gradients. Diverging from the generally held view of FID signals undergoing simple exponential decay, we show that a detailed analysis of the line shape can unravel structural geometry on much smaller scales than previously thought. While the original q-space PFG NMR relies on strong magnetic field gradients in order to achieve high spatial resolution, our current approach reaches comparable or higher resolution using much weaker gradients. As a model system, we simulated gas diffusion for xenon confined within carbon nanotubes over a range of temperatures and nanotube diameters in order to unveil manifestations of confinement in the diffusion behavior. We report a multiscale scheme that couples the above MD simulations with the generalized Langevin equation to estimate the transport properties of interest for t..., Methods for Data Collection and Processing
1. Molecular Dynamics (MD) Simulations:
The primary data for this work were generated using Molecular Dynamics (MD) simulations conducted with the open-source software package LAMMPS. The following steps outline the simulation setup and execution:
System Configuration:
Carbon nanotubes (CNTs) with radii ranging from 8 Å to 40 Å were constructed using a cylindrical lattice arrangement of carbon atoms. Xenon (Xe) gas particles were introduced into the CNTs at densities consistent with experimental conditions. The number of Xe atoms was adjusted to maintain uniform gas density across all CNT geometries.
Interaction Potentials:
The interactions between Xe atoms were modeled using a Lennard-Jones (LJ) potential with parameters \epsilon = 1.77 \, \text{kJ/mol} and \sigma = 4.1 \, \text{Å} . Similarly, Xe-CNT interactions were described using an LJ potential with \epsilon = 0.71 \, \text{kJ/mol} and \sigma = 3.7 \, \text{Å}. The carbon atoms forming t..., , # Microstructural geometry revealed by NMR lineshape analysis

[https://doi.org/10.5061/dryad.80gb5mm0t](https://doi.org/10.5061/dryad.80gb5mm0t)

## Description of the data and file structure

This dataset supports the analysis presented in the paper, *“Microstructural Geometry Revealed by NMR Lineshape Analysis”* (Niknam & Bouchard, [https://arxiv.org/abs/2410.09700](https://arxiv.org/abs/2410.09700)). The files include simulation input scripts, raw output data, logs, visual snapshots, and analysis notebooks for studying the molecular diffusion of xenon (Xe) gas inside confined carbon nanotubes (CNTs). A visualization movie of the diffusion process is also included to help interpret the results.

## **Contents**

#### **1. Simulation Input Files**

**Description**: Input files for running LAMMPS molecular dynamics (MD) simulations.

**Files**:

in.visc_cnt: LAMMPS input script to compute viscosity and simulate particle dynamics in CNTs.

nanotube.data: Data file specifying the ato...