Breakout Session: Interfaces (solid/liquid)
Abstract not provided.
Publications
Synthesis Spectroscopy and Molecular Modeling of Metal-Ligand Tracers for Characterization of Subsurface Fluid Flow
Abstract not provided.
Design and Synthesis of Novel Porous Materials for Energy and Environmental Applications
Abstract not provided.
Dissociation of sarin on a cement analogue surface: Effects of humidity and confined geometry
Journal of Physical Chemistry C
First-principles molecular dynamics simulations were used to investigate the dissociation of sarin (GB) on the calcium silicate hydrate (CSH) mineral tobermorite (TBM), a surrogate for cement. CSH minerals (including TBM) and amorphous materials of similar composition are the major components of Portland cement, the binding agent of concrete. Metadynamics simulations were used to investigate the effect of the TBM surface and confinement in a microscale pore on the mechanism and free energy of dissociation of GB. Our results indicate that both the adsorption site and the humidity of the local environment significantly affect the sarin dissociation energy. In particular, sarin dissociation in a low-water environment occurs via a dealkylation mechanism, which is consistent with previous experimental studies.
Light Gas Separations and Storage with MOFs via DFT Modeling Synthesis and Pressurized Induced Structural Changes
Abstract not provided.
Geochemistry of Interfaces: From Surfaces to Interlayers to Clusters
Abstract not provided.
Molecular Geochemistry: Atomistic Simulations of Mineral Interfaces
Abstract not provided.
Structural Thermodynamic and Transport Properties at Clay Interfaces from Molecular Simulation
Abstract not provided.
Development of Pre-processing
Abstract not provided.
DFT Modeling of Metal-Organic Frameworks for Oxygen-Nitrogen Separation
Abstract not provided.
Selective O2 Sorption at Ambient Temperatures via Node Distortions in Sc-MIL-100
Chemistry of Materials
An open pored metal-organic framework (MOF) with oxygen selectivity at exceptionally high temperatures is confirmed by synthesis, sorption, and synchrotron structural analyses. The large-pore MIL-100 framework with access to the metal center (e.g., Sc and Fe) resulted in preferential O2 over N2 gas uptake at temperatures ranging from 77 K to ambient temperatures (258, 298, and 313 K). Most notably, Sc-MIL-100 shows exceptional O2 sorption; pair distribution function analyses indicate that this is due to distortions in the framework owing to the size of Sc atoms, in particular in the trimer metal cluster. Experimental studies also correlate very well with GCMC simulations, confirming more favorable O2-framework interactions at pressures up to 1 bar, due to the close proximity of O2 to the high density of metal centers in the small tetrahedral cages. Both materials maintain their crystallinity upon gas adsorption cycling, are regenerable, and show exceptional promise for use in energy efficient oxygen purification processes, such as Pressure Swing Adsorption.
Comparison of Electrical Conductivity in Montmorillonite Interlayers and Corresponding Bulk Fluids Through Molecular Dynamics Simulation
Abstract not provided.
Ab initio molecular dynamics determination of competitive O2 vs. N2 adsorption at open metal sites of M2(dobdc)
Physical Chemistry Chemical Physics
The separation of oxygen from nitrogen using metal-organic frameworks (MOFs) is of great interest for potential pressure-swing adsorption processes for the generation of purified O2 on industrial scales. This study uses ab initio molecular dynamics (AIMD) simulations to examine for the first time the pure-gas and competitive gas adsorption of O2 and N2 in the M2(dobdc) (M = Cr, Mn, Fe) MOF series with coordinatively unsaturated metal centers. Effects of metal, temperature, and gas composition are explored. This unique application of AIMD allows us to study in detail the adsorption/desorption processes and to visualize the process of multiple guests competitively binding to coordinatively unsaturated metal sites of a MOF.
Light Gas Separations with MOFs via
Abstract not provided.
Detection of Soluble Ligand-Tuned Molecular Tags for Subterranean Fluid Flow Monitoring Using Resonance Raman Spectroscopy
Molecular dynamics simulation of diffusion and electrical conductivity in montmorillonite interlayers
Journal of Physical Chemistry C
The diffusion of water and ions in the interlayer region of smectite clay minerals represents a direct probe of the type and strength of clay-fluid interactions. Interlayer diffusion also represents an important link between molecular simulation and macroscopic experiments. Here we use molecular dynamics simulation to investigate trends in cation and water diffusion in montmorillonite interlayers, looking specifically at the effects of layer charge, interlayer cation and cation charge (sodium or calcium), water content, and temperature. For Na-montmorillonite, the largest increase in ion and water diffusion coefficients occurs between the one-layer and two-layer hydrates, corresponding to the transition from inner-sphere to outer-sphere surface complexes. Calculated activation energies for ion and water diffusion in Na-montmorillonite are similar to each other and to the water hydrogen bond energy, suggesting the breaking of water-water and water-clay hydrogen bonds as a likely mechanism for interlayer diffusion. A comparison of interlayer diffusion with that of bulk electrolyte solutions reveals a clear trend of decreasing diffusion coefficient with increasing electrolyte concentration, and in most cases the interlayer diffusion results are nearly coincident with the corresponding bulk solutions. Trends in electrical conductivities computed from the ion diffusion coefficients are also compared.
Light Gas Separations with MOFs via
Abstract not provided.
Light Gas Separations and Storage with MOFs via DFT Modeling Synthesis and Pressurized Induced Structural Changes
Abstract not provided.
Molecular Geochemistry: Atomistic Simulations of Mineral Interfaces
Abstract not provided.
Novel metal-organic frameworks for efficient stationary sources via oxyfuel combustion
Oxy-fuel combustion is a well-known approach to improve the heat transfer associated with stationary energy processes. Its overall penetration into industrial and power markets is constrained by the high cost of existing air separation technologies for generating oxygen. Cryogenic air separation is the most widely used technology for generating oxygen but is complex and expensive. Pressure swing adsorption is a competing technology that uses activated carbon, zeolites and polymer membranes for gas separations. However, it is expensive and limited to moderate purity O₂ . MOFs are cutting edge materials for gas separations at ambient pressure and room temperature, potentially revolutionizing the PSA process and providing dramatic process efficiency improvements through oxy-fuel combustion. This LDRD combined (1) MOF synthesis, (2) gas sorption testing, (3) MD simulations and crystallography of gas siting in pores for structure-property relationship, (4) combustion testing and (5) technoeconomic analysis to aid in real-world implementation.
Detection of Soluble Ligand-Tuned Molecular Tags for Subterranean Fluid Flow Monitoring Using Resonance Raman Spectroscopy
Light Gas Separations with MOFs via
Abstract not provided.
Efficient Light Gas Separations with MOFs via Predictive Modeling and Tuned Synthesis
Abstract not provided.
Methylene blue adsorption on the basal surfaces of kaolinite: Structure and thermodynamics from quantum and classical molecular simulation
Clays and Clay Minerals
Organic dyes such as methylene blue (MB) are often used in the characterization of clays and related minerals, but details of the adsorption mechanisms of such dyes are only partially understood from spectroscopic data, which indicate the presence of monomers, dimers, and higher aggregates for varying mineral surfaces. A combination of quantum (density functional theory) and classical molecular simulation methods was used to provide molecular detail of such adsorption processes, specifically the adsorption of MB onto kaolinite basal surfaces. Slab models with vacuum-terminated surfaces were used to obtain detailed structural properties and binding energies at both levels of theory, while classical molecular dynamics simulations of aqueous pores were used to characterize MB adsorption at infinite dilution and at higher concentration in which MB dimers and one-dimensional chains formed. Results for the neutral MB molecules are compared with those for the corresponding cation. Simulations of the aqueous pore indicate preferred adsorption on the hydrophobic siloxane surface, while charge-balancing chloride ions adsorb at the aluminol surface. At infinite dilution and in the gas-phase models, MB adsorbs with its primary molecular plane parallel to the siloxane surface to enhance hydrophobic interactions. Sandwiched dimers and chains are oriented perpendicular to the surface to facilitate the strong hydrophobic intermolecular interactions. Compared with quantum results, the hybrid force field predicts a weaker MB adsorption energy but a stronger dimerization energy. The structure and energetics of adsorbed MB at infinite dilution are consistent with the gas-phase binding results, which indicate that monomer adsorption is driven by strong interfacial forces rather than by the hydration properties of the dye. These results inform spectroscopic studies of MB adsorption on mineral surfaces while also revealing critical areas for development of improved hybrid force fields.
Molecular simulation of structure and diffusion at smectite-water interfaces: Using expanded clay interlayers as model nanopores
Abstract not provided.
Results 101–125 of 231