Accurate Prediction of Bond Dissociation Energies and Barrier Heights for High-Energy Caged Nitro and Nitroamino Compounds Using a Coupled Cluster Theory

Abstract

Highly accurate theoretical values of bond energies and activation barriers of primary decomposition reactions are crucial for reliable predictions of thermal decomposition and detonation-related phenomena of energetic materials (EM). However, due to the prohibitive computational cost, high-level ab initio calculations had been impractical for a large number of important EMs, including, e.g., hexanitrohexaazaisowurtzitane (CL-20). In the present work, we obtained accurate bond dissociation energies and the activation barriers for primary decomposition reactions for a series of novel promising caged polynitroamino and polynitro EMs, viz., CL-20, TEX, octanitrocubane (ONC), and hexanitro derivatives of adamantane, using the recently proposed domain-localized pair natural orbitals (DLPNO) modifications of coupled cluster techniques. DLPNO-CCSD(T) allows for routine quadruple-ζ basis set quality coupled cluster calculations for the species comprised of ∼30 non-H atoms. The benchmarks on a number of simpler congeners of CL-20 and ONC revealed that the DLPNO approach does not deteriorate the quality of the quadruple-ζ coupled cluster procedure. With the aid of this technique, the full set of gas-phase primary decomposition reactions for all 9 conformers of CL-20 was considered. For all species studied, C−NO 2 or N−NO 2 radical decomposition channels dominate over molecular counterparts. The best theoretical results reported in the literature so far, viz., density functional theory energies of nitro group radical elimination in CL-20 and ONC, underestimate the value by ∼10 kcal mol −1 . We also present reliable and accurate gas-phase formation enthalpies for CL-20, ONC, and related species. In a more general sense, these results offer a new level of predictive computational kinetics for polynitro-caged energetic materials.

Density functional theory studies of effects of boron replacement on the structure and property of RDX and HMX

“…Then, the bond dissociation energy (BDE) of weak bonds is a key factor widely used to study and compare the thermal stability of energetic compounds. [13,19,20] The higher the BDE value is, the better the thermal stability in general. For nitramines, the N NO 2 bond is the relatively weak bond generally; thus, the BDE values of (N NO 2 ) max in RDX and RDX-B2 were calculated, as found that the BDE of RDX-B2 (204.7 kJ/mol) is higher than that of RDX (153.9 kJ/mol), showing that the former compound has much better thermal stability than the latter one.…”

Nitro-, Cyano-, and Methylfuroxans, and Their Bis-Derivatives: From Green Primary to Melt-Cast Explosives

“…All computational approaches for the calculation of ∆ f H 0 (g) employed in the present work were benchmarked on a series of energetic N-rich heterocycles and exhibited an average "chemical" accuracy (~4 kJ mol −1 ) [49,54,55].…”

“…To this end, earlier, some of us proposed a "bottom-up" approach, that is, the multilevel procedures W2-F12 and/or W1-F12 in conjunction with the atomization energy approach for smaller species complemented with the domain-based local pair natural orbital coupled cluster (DLPNO-CCSD(T)) enthalpies of isodesmic reactions for medium-sized compounds [54,55]. The overall accuracy of these methods on a test set composed of nitrogen-rich heterocyclic compounds turned out to be close to "chemical" (~4 kJ mol −1 ).…”

Screening for energetic compounds based on 1,3-dinitrohexahydropyrimidine skeleton and 5-various explosopheres: molecular design and computational study

“…The strength of bonding, which could be evaluated by bond dissociation energy (BDE), is fundamental to understand pyrolysis mechanism and the thermal stability of the compound 50 , 51 . The BDE of the molecule corresponding to the enthalpy of reaction A–B(g) → A·(g) + B·(g), which is required for homolytic bond cleavage at 0 K and 1 atm, was calculated in terms of Eq.…”