Quantum tunneling instability of the mythical hexazine and pentazine

Abstract

Through computational analysis we found that pentazine and hexazine, two hypothetical high-energy density materials, exhibit inherent instability due to quantum tunneling effects. This instability remains even near the absolute zero,...

Norcaradiene–Cycloheptatriene Equilibrium: A Heavy-Atom Quantum Tunneling Case

“…This phenomenon, known as "tunneling instability", has recently been observed in systems distinct from those mentioned so far, such as hexazine, pentazine, and diazo compounds. 43,44 However, this effect has likewise been observed for molecules similar to norcaradiene, such as (11). 45 The detection of this intermediate proved to be unattainable due to its swift conversion into its isomer 12, driven by heavy-atom tunneling.…”

Quantum Tunneling Instability in Pericyclic Reactions

“…When this molecular fragility by tunneling occurs with entities that semiclassically would be stable, we called this effect quantum tunneling instability ( QTI ). − …”

“…Ideally we should also compute the large-curvature tunneling (LCT) rates to corroborate if the corner cutting of the PES is larger than what SCT can cover. However, not only LCT is intractable for systems of this size, but more importantly, our previous preliminary tests on several small systems showed that the level of corner cutting is moderate, and therefore better described by SCT for heavy atom tunnelling . See the Supporting Information for an example of Polyrate input files to see all of the applied methods and parameters.…”

Quantum Tunneling Instability in Pericyclic Reactions: The Cheletropic, Coarctate, and Ene Cases

“…With two substitutions, the molecule might be SC-unstable against degradation to HCN and N 2 [ )], with τ 1/2 lower than a second even close to 0 K. Clearly, if polinitrogenated compounds are considered as potential energetic materials, it is worthwhile to keep the tunneling effect in mind to judge their stability. 7 Ch5 is, like Ch4, a stable system. However, in its pathway, Ch5 cl is a high-energy minimum in the PES.…”

“…Such instability was thermodynamically driven by the large exothermicity of the reaction mostly obtained by using N 2 and CO as leaving groups. The critical studied aspect of these reactions was the possibility of suffering a strong kinetic acceleration thanks to their quantum tunneling instability ( QTI ). − This means that, in principle, some supposedly stable molecules according to the semiclassical ( SC ) viewpoint will in practice be unsynthesizable, unobservable, and/or unisolable as a result of tunneling.…”