Search for the Decomposition Process of 2,4,6-Trinitrotoluene by an Evolutionary Algorithm.

Area of Science:

• Computational chemistry
• Materials science
• Chemical kinetics

Background:

• 2,4,6-trinitrotoluene (TNT) is a widely used explosive.
• Understanding TNT decomposition pathways is crucial for safety and material science.
• Previous studies have explored TNT stability, but detailed mechanisms with radical interactions are less understood.

Purpose of the Study:

• To explore stable states in 2,4,6-trinitrotoluene (TNT) crystal systems with added hydrogen radicals (H_add).
• To gain insights into the decomposition process of TNT using computational methods.
• To identify the optimal number of H_add's for maximum energy reduction in TNT systems.

Main Methods:

• Utilized a structure-search scheme based on first-principles calculations.
• Employed an evolutionary algorithm (EA) with three operators (displacement, permutation, mating) acting on H_add's.
• Investigated systems with varying numbers of H_add's (n=1-8) and constructed formation energy convex-hull diagrams.

Main Results:

• Identified the system with n=6 H_add's as having the largest energy reduction.
• Observed the transformation of five out of eight TNT molecules into various products, including NO, H₂O, and complex organic compounds.
• Analyzed structural transformations, noting H_add's react with C, N, and O in TNT, forming six-membered rings and leading to partial decomposition.

Conclusions:

• The addition of hydrogen radicals significantly impacts TNT stability and decomposition pathways.
• A specific concentration of H_add's (n=6) leads to substantial energy reduction and molecular transformation.
• The decomposition mechanism involves initial reactions of H_add's with TNT components, followed by bonding of partially decomposed fragments.