KIT - Campus North -
Lecture Hall 0-167, Bldg. 640

21.10.2009

Dr. Ir. Gilles de Wijs
Electronic Structure of Materials
Radboud University Nijmegen, The Netherlands

10:00

Abstract: We report on the current status of the implementation of NMR parameters, electric field gradients and chemical shifts, in the first-principles electronic structure programme VASP (Vienna Ab initio Simulation Package). In a study of EFGs of AlxGa1-xAs, a zincblende compound with (partial) disorder in the occupancy of the cation lattice, distributions of EFGs could be accurately modelled using a special kind of additivity. These distributions, that arise from disorder in distant coordination shells, are well-described with a modified Czjzek distribution. Connection with experiment, carried out in the Nijmegen NMR group (Kentgens) is made. To calculate chemical shifts VASP allows finite field GIPAW calculations in a saw-tooth vector potential for molecules. For shift calculations on periodic systems VASP follows the recently introduced converse approach by Thonhauser et al. [J. Phys. Chem., 2009] using norm-conserving GIPAW. We'll discuss this approach, provide benchmark calculations on small molecules, and present first DFT results on the organic crystals of Venlafaxine and Isocyanocarbazole. Contact with experiment is made and the peculiar hydrogen bonding in the latter crystal is discussed.