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A comparative study of nitrogen physisorption on different C70 crystal structures using an ab initio based potential
Gaurav Arora1, Jeffery B Klauda, Stanley I Sandler
1Center for Molecular and Engineering Thermodynamics, Department of Chemical Engineering, University of Delaware, Newark, DE 19716, USA.
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
This study determined atom site Lennard-Jones potential parameters for nitrogen interacting with C(70) fullerene. Grand canonical Monte Carlo simulations revealed distinct adsorption properties on various C(70) crystal structures.
Area of Science:
- Computational Chemistry
- Materials Science
- Physical Chemistry
Background:
- Accurate modeling of gas adsorption on novel carbon nanomaterials is crucial for applications in gas storage and separation.
- Fullerenes, such as C(70), present unique surface geometries and electronic properties that influence adsorbate interactions.
- Understanding nitrogen adsorption on C(70) requires precise interatomic potentials derived from first-principles calculations.
Purpose of the Study:
- To determine accurate Lennard-Jones potential parameters for nitrogen-carbon interactions on C(70) surfaces using quantum mechanical calculations.
- To investigate the surface adsorption properties of molecular nitrogen (N(2)) on five different C(70) crystal structures using grand canonical Monte Carlo (GCMC) simulations.
- To compare adsorption behavior predicted by C(70)-specific potentials with those derived from planar graphite.
Main Methods:
- Ab initio based hybrid method for calculating interaction energies to derive Lennard-Jones parameters.
- Grand canonical Monte Carlo (GCMC) simulations to model N(2) adsorption isotherms.
- Utilizing five distinct C(70) crystal structures: rhombohedral, face-centered cubic (fcc), hexagonal close-packed (hcp) ideal, hcp deformed, and monoclinic.
Main Results:
- Lennard-Jones parameters for N-C interactions on C(70) differ from those on planar graphite due to C(70)'s curvature and pentagonal rings.
- Simulations show significant differences in adsorption properties, especially at low N(2) coverage, highlighting the importance of N-C interactions.
- Surface area, monolayer capacity, and isosteric heat of adsorption vary considerably across different C(70) crystal structures, influenced by phase transformations.
Conclusions:
- The developed ab initio based potential accurately captures N(2)-C(70) interactions, outperforming generic graphite potentials for fullerene adsorption.
- The structural diversity of C(70) crystals leads to distinct adsorption behaviors, impacting the material's capacity for nitrogen uptake.
- Shear-induced phase transformations in C(70) lattices significantly affect adsorption characteristics, underscoring the need for structure-specific modeling.