Structures and molecular surface electrostatic potentials of high-density C, N, H systems

Tri-s-triazine and two ditetrazolodiazines are known to have unusually high crystal densities (for unsubstituted C, N, H compounds). We have used a nonlocal density functional procedure to compute the geometries and energies of these and three related molecules, and then calculated the ab initio SCF electrostatic potentials on their molecular surfaces. We attribute the high densities to the relatively small molecular volumes and the strong intermolecular attractions arising from highly varying surface potentials. The energy differences of the two ditetrazoles and their diazide tautomers were computed, as well as for the dinitro derivative of one of the former.