ORIENTATIONAL ORDERING OF FRUSTRATED MOLECULAR QUADRUPOLES - NMR-STUDIES OF N-2 AR SOLID MIXTURES

We report NMR studies of the effect of lattice geometry on the orienta tional ordering of N-15(2) molecules in solid N-2-Ar mixtures. The N-2 molecules interact through highly frustrated electrostatic quadrupole -quadrupole interactions and samples with 50% N-2 that form fee lattic es show evidence for long range order with a very small distribution o f order parameters in contrast to the quadrupolar glass phase observed for the hcp lattice at higher concentrations (57%-77%).