Early chemistry in hot and dense nitromethane:Molecular dynamics simulations

摘要

We report density functional molecular dynamic simulations to determine the early chemical events of hot (T=3000 K) and dense (rho=1.97 g/cm~3,V/V_0=0.68) nitromethane (CH_3NO_2).The first step in the decomposition process is an intermolecular proton abstraction mechanism that leads to the formation of CH_3NO_2H~+ and the aci ion H_2CNO_2~- . This event is also confirmed to occur in a fast annealing simulation to a final temperature of 4000 K at p=2.20 g/cm~3.An intramolecular hydrogen transfer that transforms nitromethane into the aci acid form,CH_2NO_2H,accompanies this event.To our knowledge,this is the first confirmation of chemical reactivity with bond selectivity for an energetic material near the Chapman-Jouget state of the fully reacted material.We also report the decomposition mechanism followed up to the formation of H_2O as the first stable product.We note that similarities in the global features of reactants,intermediates,and products of the reacting fluid seem to indicate a threshold for similar chemistry in the range of high densities and temperatures reported herein.