Structure and Dynamics of Ca in Clays, Mineral Phases of Concrete, and Ca-NOM Complexes: Combined Natural Abundance 43Ca NMR and Computational Molecular Modeling Studies
EMSL Project ID
30208
Abstract
The objective of this research is to use natural abundance 43Ca NMR and molecular dynamics (MD) modeling to study Ca2+ structure and dynamics in environmentally and technologically important materials, including Ca-saturated clays, calcium silicate hydrate (CSH) minerals, and Ca-bearing natural organic matter (NOM) complexes. Ca2+ is critical to the behavior of these materials as well as to a wide range of geobiological, biochemical and biomedical issues, but Ca2+ structure and dynamics are seldom studied on the molecular-level with a combined experimental and modeling approach. Solid-state NMR spectroscopy has significant potential in this regard, but the only NMR-active calcium isotope (43Ca) has spin I = 7/2 and suffers from severe sensitivity limitations due to its small natural abundance (sensitivity relative to 13C = 0.05). Nevertheless, recent research has shown that 43Ca line-widths are relatively narrow and that large sample volumes and moderately high magnetic fields (14.1 T) enable rather efficient natural abundance 43Ca NMR studies of crystalline inorganic and organic Ca compounds. The sensitivity benefits of the high magnetic fields available at PNNL combined with sensitivity-enhancing pulse sequences should allow for natural abundance 43Ca NMR studies in more complex systems of environmental relevance. The experimental NMR efforts will be complemented and supported by molecular dynamics computer simulations of the same systems using EMSL Chinook and NWChem. By combining NMR and computations, we will be able to quantify structural and dynamic characteristics of Ca2+ interactions with basal crystallographic planes of clays and CSH phases and with the acidic groups of NOM in aqueous environments over several important time and length scales. Due to the novelty of the methods/applications and importance of Ca2+ in materials, environmental chemistry, and biology/biochemistry, we anticipate this research will lead to several high-impact publications.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2009-01-02
End Date
2011-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Bowers GM, and RJ Kirkpatrick. 2009. "Natural Abundance 43Ca NMR Spectroscopy of Tobermorite and Jennite: Model Compounds for C–S–H." Journal of the American Ceramic Society 92(2):545-548. doi:10.1111/j.1551-2916.2008.02906.x
Bowers GM, and RJ Kirkpatrick. 2011. "Natural Abundance 43Ca NMR as a Tool for Exploring Calcium Biomineralization: Renal Stone Formation and Growth." Crystal Growth & Design 11(12):5188-5191. doi:10.1021/cg201227f
Singer JW, AO Yazaydin, RJ Kirkpatrick, and GM Bowers. 2012. "Structure and Transformation of Amorphous Calcium Carbonate: A Solid-State 43Ca NMR and Computational Molecular Dynamics Investigation." Chemistry of Materials. doi:10.1021/cm300389q