Motivation

In order to understand the chemical bonding of intermetallic compounds, the characterization of structural details is highly important. Since structural disorder is frequently observed in intermetallic compounds, strategies and tools have to be developed which compensate the restrictions of diffraction methods. Nuclear magnetic resonance (NMR) spectroscopy as a local probe has been shown to be highly suited for the investigation of disordered materials for example in electrically non-conducting glasses [1]. However, for samples showing metallic conductivity several NMR relevant couplings arise [2] and strategies, being suitable for glasses, can not be used without further modification.

NMR spectroscopic approach

Our main research interest is the usage and establishment of solid-state NMR spectroscopy as a local probe for the detection, analysis and understanding of disorder phenomena in intermetallic compounds.
Besides shift interactions (chemical shielding and Knight shift) large quadrupole coupling often dominates the NMR signals of intermetallic compounds. The quadrupole coupling is caused by the interaction of the nuclear quadrupole moment (Q) with the electric field gradient (EFG) in a noncubic environment and can be described by the quadrupole coupling constant (C_Q).
The EFG is a measure of the anisotropy of the charge distribution around a nucleus. Therefore, it is very sensitive to the local chemical bonding situation. In this regard the NMR spectroscopic determination of the EFG provides experimental information about the chemical bonding situation in intermetallic compounds.
This can be correlated with results of quantum mechanical calculations of the EFG. The link of NMR experiment and theory gives access to structural research as well as an experimental proof of the model used for the quantum mechanical calculations [3].

More detailed information

F. Haarmann. Quadrupolar NMR of Intermetallic Compounds. In R. K. Harris, R. E. Wasylishen, Editors, Enzyclopedia of Magnetic Resonance. John Wiley & Sons, Ltd, Chichester (2011).

Haarmann et al. Scientific Report MPI CPfS 2009.
"Quadrupole Coupling - the Key to NMR Spectroscopy of Intermetallic Compounds."

Haarmann et al. Tätigkeitsbericht MPI CPfS 2009.
 "Kernspin-Resonanz-Spektroskopie als lokale Sonde: Untersuchungen zu Struktur und Magentismus intermetallischer Phasen."

References

[1] H. Eckert Bunsen-Magazin 2008,10(5),159.
"Solid state nuclear magnetic resonance: a versatile tool in solid state chemistry and material science."
[2] C. P. Slichter Principles of Magnetic Resonance, 3rd ed. 1990, Springer Verlag, Berlin, Heidelberg, New York.
[3] F. Haarmann, K. Koch, D. Grüner, W. Schnelle, O. Pecher, R. Cardoso-Gil, H. Borrmann, H. Rosner, Yu. Grin Chem. Eur. J. 2009, 15, 1673.
"Electronic Structure, Chemical Bonding, and Solid-State NMR Spectroscopy of the Digallides of Ca, Sr, and Ba."