Molecular Simulation of Reaction Mechanisms and Transition States

Molecular simulations provide profound insight into the atomic and molecular mechanisms that determine the behavior of materials. A particular tool for this purpose is DMol3. It is a density functional theory (DFT) quantum mechanical program included in the Materials StudioTM software package. The methodological aspects of using DMol3 to study the decomposition of energetic materials or their components through the identification of transition states and the calculation of activation energies are presented. The initial step in utilizing DMol3 is the geometric optimization of the molecules involved in the reaction. The optimization process is followed by the search for transition states, which represent the molecular configurations on the reaction pathway. To achieve this, DMol3 employs a range of algorithms with the objective of identifying the energy barriers between the reactants and products. These barriers, also known as activation energies, are of great significance in the comprehension of reaction kinetics. An example of a complex reaction behavior is the curing of CTPB (carboxyl-terminated polybutadiene) with aziridine-type curing agents, such as MAPO (tris[1-(2-methylaziridinyl)] phosphane oxide). MAPO displays distinctive behavior, exhibiting not only the primary curing reaction but also the splitting of the binder network through the breaking of N-P bonds within its chemical framework by attack of water. This bond breaking is investigated using DMol3.