First-Principles Calculation of Electric Field Gradients in Metals, Semiconductors, and Insulators
J. W. Zwanziger and M. Torrent
A scheme for computing electric field gradients within the projector augmented wave (PAW) formalism of density functional theory is presented. On the basis of earlier work (M. Profeta, F. Mauri, C.J. Pickard, J. Am. Chem. Soc. 125, 541, 2003) the present implementation handles metallic cases as well as insulators and semiconductors with equal efficiency. Details of the implementation, as well as applications and the discussion of the limitations of the PAW method for computing electric field gradients are presented.
A Quantum-Chemical Investigation of the Geometry and NMR Chemical Shifts of Bilirubin
T. Metzroth, M. Lenhart and J. Gauss
A computational investigation using density-functional-theory methods has been performed concerning the structure and nuclear magnetic resonance (NMR) chemical shifts of bilirubin with a special emphasis on the hydrogen bonds. Solid-state effects on the NMR spectra are investigated by considering a trimeric model derived from the available X-ray structure. Satisfactory agreement between theory and experiment is found with ring-current effects playing only a minor role for the interpretation of the solid-state NMR spectra.