QUADRUPOLE COUPLING ASSIGNMENTS IN INORGANIC PERIODIC-SYSTEMS BY AB-INITIO CALCULATION OF ELECTRIC-FIELD GRADIENTS

Ab initio SCF calculations were performed in the unit cell environment , making use of the periodic behaviour to compute a wave-function for the bulk material. Electric field gradient (EFG) calculations were per formed on the resulting wave-functions, and these are compared with ex perimental quadrupole coupling parameters. Examples of inorganic molec ular and ionic crystals (nitrogen, chlorine and lithium nitride) and m inerals or partially covalent lattice structures (alumina, petalite, a lpha-quartz, boron oxide, boron nitride and sulphur nitride) are descr ibed. The effects of the basis set in these calculations are considere d, and the limitations imposed by the nature of the calculation are de scribed.