Ab initio simulation of the solid state for /sup 14/N NQR assignments

Detailed analysis of the microwave spectra (MW) of gases can yield the complete /sup 14/N quadrupole coupling tensor, with signs, magnitudes and directions; and only inertial axis (IA) data is obtained. In contrast /sup 14/N nuclear quadrupole resonance (NQR) leads to the diagonalised tensor, but only with relative signs and no directions. Ab initio SCF calculations with a double zeta or better basis yield good values when compared with MW data for single molecules. In order to assign /sup 14/N NQR data the crystal structure must be known. The application to various H-bonded systems with heterocyclic rings is described