Intermolecular Interactions in Highly Disordered, Confined Dense N2.

Molecular nitrogen is a benchmark system for condensed matter and, in particular, for looking at universal properties of strongly confined dense systems. We conducted Raman and X-ray diffraction measurements on a dense and disordered form of molecular nitrogen subnanoconfined in a noncatalytic pure SiO2 zeolite under pressure, up to 50 GPa. In this form, N2-N2 interactions and, consequently, distances are found to be very close to those of bulk N2 and intramolecular interactions progressively weaken upon increasing pressure. Surprisingly, the filled zeolite is still crystalline at 50 GPa with silicon in tetrahedral coordination by oxygen, which is a record pressure for this type of coordination among all the known forms of silica. We have thus found a rationale for the polymerization of a number molecules occurring in the microchannels of noncatalytic zeolites under pressure, where the pressure threshold is found to be very similar to that observed in bulk samples.