DFT Studies on a Series of Nitramines Containing Pyridine Ring

Abstract

In this article, a series of nitramines containing pyridine ring were studied by density functional theory (DFT). The gas-phase heats of formation were predicted based on the isodesmic reactions and the condensed-phase heats of formation and heats of sublimation were estimated with the Politzer's approach. The detonation velocity and pressure were calculated using the empirical Kamlet-Jacobs equation. Many title compounds have better performance than RDX (hexahydro-1,3,5-trinitro-1,3,5-trizine) and HMX (1,3,5,7-tetranitro-1,3,5,7- tetraazacyclooctane). The impact sensitivity was evaluated with the characteristic height (h50). It is found that most of the studied compounds have lower sensitivities than CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12- hexaazaisowurtzitane). The crystal structures were predicted with the molecular mechanics method and optimized by the CA-PZ local density approximation of DFT. Analysis of the crystal energy gap indicates I-13, II-1, III-1, and IV-1 are nearly conductors and other compounds are semiconductors. For I-1∼I-8 and I-11, the largest contribution to the valence bands is mainly from the p states of the C and N atoms in the pyridine and fused ring and for the other compounds, from the p states of the C and N atoms in the amino group and pyridine.