arXiv subjects

Samuel Mathews

Publications and source records attributed to Samuel Mathews.

4 recordsLinked to original sources

arXiv2026

Atomistic Modeling of Methane and Carbon Dioxide Structure I Gas Hydrates Under Pressure: Guest Effects and Properties

Gas hydrates are potential candidates in future energy sources while simultaneously providing structures with extensive applications in carbon capture and storage, gas transport, and important separation processes. Prior research in the field considers the dynamics of the water molecule backbone in particular. We investigated the pressure-enthalpy landscape and mechanical stability envelope of sI methane and carbon dioxide hydrates simulated using DFT. We investigated the effect of the revPBE + DFT-D2 and the SCAN + rVV10 and their treatment of the exchange correlation interactions. We examined the zero pressure material properties, finding that revPBE comparatively underbinds the interactions, causing more flexible structures with large equilibrium volumes. Under pressure, the carbon dioxide molecule was found to align itself parallel to the hexagonal faces of the large cage despite the functional used. Additionally, the property differences are caused by the ability of the carbon dioxide molecule to rotate and disperse the changes in the energy landscape in ways that methane molecules cannot. This computational methodology describes the elastic stability of gas hydrate, marginal stability, and critical differences across important molecular interactions, confirming experimentally observed restrictions in guest molecule rotations and novel pressure behaviors under hydrostatic loads

physics.chem-ph↗

arXiv2025

Periodic feature characterization in nanostructured surfaces and emulsions

Understanding structure-function relationships is essential to advance the manufacturing of next-gen materials with desired properties and functionalities. Precise and rapid measurement of features like wrinkle size, droplet diameter, and surface roughness is essential to establishing such structure-function relationships. To this end, this work developed feature size and surface morphology characterizations through image analysis in Python and validated them with both synthetic and experimental images. Manual measurements of bio-based surfaces resulted in between 3.3% (N=50, visually simple) and 51.2% error (N=100, visually complex) compared to Python analysis results. This analysis was also used to accurately distinguish multiple feature size populations in a given image (which were missed entirely in manual measurements), and to determine the skewness and kurtosis of biological surfaces in a surface roughness map. This work contributes to a larger goal of developing a robust and computationally cheap platform to analyze complex materials to accelerate structure-function discovery.

physics.app-ph↗

arXiv2024

Molecular dynamics characterization of the interfacial structure and forces of the methane-ethane sII gas hydrate interface

The nucleation of gas hydrates is of great interest in flow assurance, global energy demand, and carbon capture and storage. A complex molecular understanding is critical to control hydrate nucleation and growth in the context of potential applications. Molecular dynamics is employed in this work combined with the mechanical definition of surface tension to assess the surface stresses that control some of the behavior at the interface. Ensuring careful sampling and simulation behavior, this work extracts meaningful results from molecular properties. We characterize the interfacial tension for sII methane/ethane hydrate and gas mixtures for different temperatures and pressures. We find that the surface tension trends positively with temperature in a balance of water-solid and water-gas interactions. The molecular dipole shows the complexities of water molecule behavior in small, compressed pre-melting layer that emerges as a quasi-liquid. These behaviors contribute to the developing knowledge base surrounding practical applications of this interface.

physics.app-ph↗

arXiv2023

Molecular dynamics predictions of transport properties for carbon dioxide hydrates under pre-nucleation conditions using TIP4P/Ice water and EPM2, TraPPE, and Zhang carbon dioxide potentials

(1) Introduction: New technologies that leverage gas hydrates phenomena include carbon capture and sequestrations. These processes are often semi-continuous and require regulation of the system's flow properties for proper operation. Accurate computational models for the viscosity of carbon dioxide hydrate systems at pre-nucleation conditions can be important for process design and control of such technologies. (2) Methods: This work validates the viscosity predictions of molecular dynamics simulations using previously measured experimental data. The TIP4P/Ice force field was used to model water, while the EPM2, TraPPE, and Zhang force fields were used for carbon dioxide. The Green-Kubo and Einstein formulations of viscosity and diffusivity were used in this work. (3) Results: All force fields overpredicted viscosity when compared to experimental data, but EPM2 resulted in lower discrepancies. Additionally, EPM2 was determined to model molecular behavior expected from the macroscopic trends in viscosity with respect to temperature and pressure. (4) Conclusions: The EPM2 force field more accurately predicted the viscosity of carbon dioxide hydrates systems at pre-nucleation conditions relative to TraPPE and Zhang.

physics.app-ph↗