Clay Mineral Surface Geochemistry group

Current Research Team

Ian Bourg

Ian C. Bourg  (Group Lead)
Research Scientist,
Earth Sciences Division,
Berkeley National Lab

Frontispiece

 

Top left: Molecular dynamics "snapshot" of water molecules (blue and white), sodium ions (purple), and methane molecules (yellow-brown) intercalated simultaneously between two layers of montmorillonite, a common smectite clay mineral [figure used for the cover of S.A. Auerbach, K.A. Carrado, and P.K. Dutta (eds.), Handbook of Layered Materials Science and Technology, Marcel Dekker, New York, 2004].

Top right: Molecular dynamics snapshot of a water-filled 4-nm-diameter cylindrical pore in a slab of silica glass (yellow, red, and white: Si, O, and H atoms in the silica structure; dark and light blue: water O and H atoms). Silanol OH groups are highlighted as red and white spheres.

Center left: Molecular dynamics snapshot of a 40Ar atom (in green) and water molecules located in its first solvation shell.

Center right: Molecular dynamics snapshot of the interface between aqueous brine and supercritical CO2 (water O and H atoms in red and white, Na+ and Cl- ions in blue and red, CO2 molecules in gray). The pink line shows the trajectory of a water molecule evaporating into the CO2 phase.

Bottom left: Molecular dynamics snapshots of a CO2 hydrate clathrate equilibrated with liquid water at 280, 283, and 289 K (from top to bottom).

Bottom right: Molecular dynamics snapshot showing different populations of water molecules in the first two statistical water monolayers on a smectite clay surface (purple, red, and orange: first-layer water molecules donating two, one, or zero hydrogen bonds to siloxane surface O atoms; pink: second-layer water molecules). The dark and light blue spheres are Na+ and Ca2+ outer-sphere surface complexes.

 

Amy Hofmann

Amy Hofmann 
Assistant Professor,
Franklin & Marshall College

Michael Holmboe

Michael Holmboe 
Berkeley Lab Affiliate,
Postdoctoral Fellow,
Uppsala University, Sweden

Kideok Kwon

Kideok Kwon 
Assistant Professor,
Kangwon National University, South Korea

Yangyang Liu

Yangyang Liu 
Berkeley Lab Affiliate,
Research Scientist,
British Petroleum

Aric Newton

Aric Newton 
Postdoctoral Fellow,
Hokkaido University

Laura Nielsen

Laura Nielsen 
Postdoctoral Fellow,
Stanford University

Keith Refson

Keith Refson 
Scientist,
Rutherford-Appleton Laboratory, UK

Garrison Sposito

Garrison Sposito
Faculty Senior Scientist,
Earth Sciences Division, Berkeley National Laboratory

Research Goals

Because of their ubiquitous presence in natural materials and their strong surface reactions, nanoparticles produced by weathering or biological processes in natural settings (in particular, clay minerals) figure importantly in a broad range of environmental phenomena, from global climate change to contaminant remediation. Our research is designed to provide molecular-scale information about the surface chemistry of these nanoparticles based on state-of-the-art computer simulation using tested codes and realistic models of layer type minerals. These computer simulations are powerful complements to experimental methods, in that they can reveal the behavior of individual atoms in complex geochemical systems and the manner in which molecular-scale interactions give rise to complex properties such as adsorption, wetting, molecular diffusion, ligand exchange kinetics, nanoparticle electronic structure, and the electrostatic screening of charged surfaces.

Methods

We have been developing an approach to the surface geochemistry of smectite, Si oxide, Mn oxide, and Fe sulfide minerals based on molecular-level simulation. Our research, supported by the DOE-BES program at Lawrence Berkeley National Laboratory, is aimed at understanding the mechanisms by which these minerals interact with water molecules, cations, organic molecules, and supercritical CO2 in aqueous subsurface environments. Our principal techniques, molecular dynamics (MD) and density functional theory (DFT) simulations, are well-established, essential components of research in theoretical physical chemistry.

The underlying approach in MD simulations is to construct potential functions that model all of the known interactions in a system of ions, atoms, and molecules, then devise a strategy for sampling the phase space of the interacting system in order to compute its properties. In a MD simulation, the phase space of the system is sampled through numerical integration of the Newton-Euler equations of motion for each molecular species, which is performed consistently with the suite of potential functions assumed.

In recent years the interpretation of both diffraction and spectroscopic data on clay minerals has been facilitated by a class of independent, first-principles (sometimes termed "ab initio") quantum-mechanical simulations, which now have achieved sufficient accuracy to predict crystallographic properties of clay minerals without recourse to empirical parameterization. The ingredients of this scheme are the atomic nuclei and electrons whose interactions are described by the density functional theory (DFT) formulation of quantum mechanics. DFT-based methods are able to describe structure and bonding properties to a high degree of accuracy, including structural trends. Indeed, these methods represent the only practical quantum-mechanical approach for studying complex materials such as clay minerals and metal oxides.

Our MD calculations utilize the codes MOLDY, developed by K. Refson, and LAMMPS, distributed by Sandia National Laboratories. Our ab initio calculations are performed using a parallel version of the code CASTEP, developed by the UKCP (United Kingdom Car-Parrinello) consortium. Numerical calculations have been carried out under DOE support on Cray XT4, Cray XE6, and IBM iDataPlex supercomputers at the NERSC (National Energy Research Scientific Computing Center).

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Research Projects

Recent Publications (2011-2014)

  • Eiler JM, Bergquist B, Bourg IC, Cartigny P, Farquhar J, Gagnon AC, Guo W, Halevy I, Hofmann AE, Levin N, Schauble EA, Stolper D. Frontiers of stable isotope geoscience. Chem. Geol. 372, 119-143 (2014). [doi]
  • Holmboe M, Bourg IC. Molecular dynamics simulations of water and sodium diffusion in smectite interlayer nanopores as a function of pore size and temperature. J. Phys. Chem. C 118, 1001-1013 (2014). [doi]
  • Smit B, Reimer JA, Oldenburg CM, Bourg IC. Introduction to Carbon Capture and Sequestration. The Berkeley Lectures on Energy, Vol. 1. Imperial College Press (2014). [World Scientific Press] [Amazon]
  • Hamm LM, Bourg IC, Wallace AF, Rotenberg B. Molecular simulation of CO2- and CO3-brine-mineral systems. In: Geochemistry of Geologic CO2 Sequestration (DJ DePaolo, DR Cole, A Navrotsky, & IC Bourg, eds.), Reviews in Mineralogy & Geochemistry, Vol. 77. Mineralogical Society of America (2013). [doi]
  • DePaolo DJ, Cole DR, Navrotsky A, Bourg IC (Eds.). Geochemistry of Geologic CO2 Sequestration. Reviews in Mineralogy & Geochemistry, Vol. 77. Mineralogical Society of America (2013). [Geoscienceworld] [Mineralogical Society of America]
  • Hofmann AE, Bourg IC & DePaolo DJ. Ion desolvation as a mechanism for kinetic isotope fractionation in aqueous systems. Proc. Natl. Acad. Sci. U.S.A. 109, 18689-18694 (2012). [doi]
  • Bourg IC & Steefel CI. Molecular dynamics simulations of water structure and diffusion in silica nanopores. J. Phys. Chem. C 116, 11556-11564 (2012). [doi]
  • Nielsen LC, Bourg IC & Sposito G. Predicting CO2-water interfacial tension under pressure and temperature conditions of geologic CO2 storage. Geochim. Cosmochim. Acta 81, 28-38 (2012). [doi]
  • Bourg IC & Sposito G. Ion exchange phenomena. In: Handbook of Soil Science, Properties and Processes, 2nd ed. (PM Huang, Y Li, & ME Sumner, eds.), CRC Press, Boca Raton, Chapter 16 (2011) .
  • Bourg IC & Sposito G. Molecular dynamics simulations of the electrical double layer on smectite surfaces contacting concentrated mixed electrolyte (NaCl-CaCl2) solutions. J. Colloid Interface Sci. 360, 701-715 (2011). [doi]
  • Kwon  KD, Refson K, Bone S, Qiao R, Yang W, Liu Z, Sposito G. Magnetic ordering in mackinawite (tetragonal FeS): evidence for  strong itinerant spin fluctuations. Phys. Rev. B 83, 064402 (2011). [doi]

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