Spin polarization and dispersion effects in emergence of roaming transition state for nitrobenzene isomerization

Abstract

Since roaming was found as a new but common reaction path of isomerization, many of its properties, especially those of roaming transition state (TSR), have been studied recently on many systems. However, the mechanism of roaming is still not clear at the atomic level. In this work, we used first-principles calculations to illustrate the detailed structure of TSR in an internal isomerization process of nitrobenzene. The calculations distinctively show its nature of antiferromagnetic coupling between two roaming fragments. Moreover, the effect of dispersion is also revealed as an important issue for the stability of the TSR. Our work provides a new insight from the view of electronic structure towards the TSR and contributes to the basic understanding of the roaming systems. 82.20.Db Roaming, as a newly discovered chemical reaction path, different from the conventional ones, [1] plays an important role in the isomerization process in many systems, [2][3][4][5][6][7][8][9][10] which has broadened our sight of view towards the reaction path. As a transition state (TS) in the roaming reaction path, roaming transition state (TSR) take a critical place in the process, [11] for which its configuration and electronic structural properties have drawn a lot of attention. However, for experimental approaches, only indirect information could be observed from TSR and even normal TS. Besides, the differences between TSR and other conventional TS [12,13] are not clearly revealed in the atomic level, for which we hope to understand the mechanism in this work. PACS:Nitrobenzene is one of the typical energetic materials whose geometries and spectrum properties, isomerization and even dissociation channels have been studied theoretically and experimentally [14][15][16][17][18][19] . Recently, a new reaction channel in the 

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