Theoretical investigations on structure, density, detonation properties, and sensitivity of the derivatives of PYX.

The -NH(2), -NO(2), -N(3), -NHNO(2), and -ONO(2) substitution derivatives of PYX (2,6-bis(picrylamino)-3,5-dinitropyridine) were studied at the B3LYP/6-31G** level of density functional theory. The sublimation enthalpies and heats of formation (HOFs) in gas phase and solid state of these compounds were calculated. The theoretical predicted density (ρ), detonation pressure (P), and detonation velocity (D) showed that these derivatives have better detonation performance than PYX. The effects of substituent groups on HOF, ρ, P, and D were discussed. The order of contribution of various groups to P and D was -ONO(2) > -NO(2) > -NHNO(2) > -N(3) > -NH(2). Sensitivity was evaluated using the frontier orbital energies, bond orders, bond dissociation enthalpies (BDEs), and characteristic heights (h(50)). The trigger bonds in the pyrolysis process for these PYX derivatives may be Ring-NO(2), NH-NO(2), or O-NO(2) varying with the substituents. The h(50) of most compounds are larger than that of CL-20, and those of -NH(2), -NO(2), and most -ONO(2) derivatives are larger than that of RDX. The BDEs of the trigger bonds of all but the -ONO(2) derivatives are sufficiently large. Taking both detonation performance and sensitivity into consideration, some derivatives of PYX may be good candidates of explosives.