Sequential Molecular Dynamics Simulations: A Strategy for Complex Chemical Reactions and a Case Study on the Graphitization of Cooked 1,3,5-Triamino-2,4,6-trinitrobenzene

CY Zhang and YS Wen and XG Xue and J Liu and Y Ma and XD He and XP Long, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 25237-25245 (2016).

DOI: 10.1021/acs.jpcc.6b08227

The fundamental core of chemistry is to create new substances, and numerous complex reactions may be involved in chemical conversions. Nevertheless, clarifying the mechanisms of these complex reactions remains challenging, thereby causing insufficiencies in the fundamentals to guide new substance creation. This work proposes and emphasizes a strategy of sequential molecular dynamics simulations (SMDSs) toward complex chemical reactions. The strategy is successfully demonstrated by clarifying a complex graphitization process of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), whose mechanism has not been imaged by a single simulation alone. We conducted SMDSs with a molecular reactive force field, ReaxFF, to resemble the cook-off of TATB, i.e., a sequence of heating, expansion, and cooling acting on TATB. Graphitization is found to sequentially undergo TATB molecular decay, clustering, cluster enlargement to C sheets (sheeting), and layered stacking of C sheets, along with phase separation. Moreover, the structures graphitized from TATB can be imaged only when simulations are conducted in the sequence of heating, expansion, and cooling, in accordance with the actual conditions of cooking TATB. This successful exemplification shows that a large number of complex reaction mechanisms can be revealed using the SMDS strategy and computation ability promotion, in combination with the clarified experimental conditions. This strategy exhibits considerable potential for future use.

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