TY - JOUR

T1 - Accurate Prediction of Bond Dissociation Energies and Barrier Heights for High-Energy Caged Nitro and Nitroamino Compounds Using a Coupled Cluster Theory

AU - Kiselev, Vitaly G.

AU - Goldsmith, C. Franklin

PY - 2019/6/13

Y1 - 2019/6/13

N2 - 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-NO2 or N-NO2 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.

AB - 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-NO2 or N-NO2 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.

KW - MOLECULAR-DYNAMICS SIMULATION

KW - THERMAL-DECOMPOSITION

KW - THERMODYNAMIC PROPERTIES

KW - KINETICS

KW - MECHANISMS

KW - CL-20

KW - DENSITY

KW - 2,4,6,8,10,12-HEXANITRO-2,4,6,8,10,12-HEXAAZAISOWURTZITANE

KW - 2,2,4,4,6,6-HEXANITROADAMANTANE

KW - OCTANITROCUBANE

UR - http://www.scopus.com/inward/record.url?scp=85067509420&partnerID=8YFLogxK

U2 - 10.1021/acs.jpca.9b01506

DO - 10.1021/acs.jpca.9b01506

M3 - Article

C2 - 30920217

AN - SCOPUS:85067509420

VL - 123

SP - 4883

EP - 4890

JO - Journal of Physical Chemistry A

JF - Journal of Physical Chemistry A

SN - 1089-5639

IS - 23

ER -