Chemical reaction dynamics of PeCB and TCDD decomposition: A tight-binding quantum chemical molecular dynamics study with first-principles parameterization

The decomposition reaction dynamics of 2,3,4,4′,5-penta-chlorinated biphenyl (2,3,4,4′,5-PeCB), 3,3′,4,4′,5-penta-chlorinated biphenyl (3,3′,4,4′,5-PeCB), and 2,3,7,8-tetra-chlorinated dibenzo-p-dioxin (2,3,7,8-TCDD) was clarified for the first time at atomic and electronic levels, using our novel tight-binding quantum chemical molecular dynamics method with first-principles parameterization. The calculation speed of our new method is over 5000 times faster than that of the conventional first-principles molecular dynamics method. We confirmed that the structure, energy, and electronic states of the above molecules calculated by our new method are quantitatively consistent with those by first-principles calculations. After the confirmation of our methodology, we investigated the decomposition reaction dynamics of the above molecules and the calculated dynamic behaviors indicate that the oxidation of the 2,3,4,4′,5-PeCB, 3,3′,4,4′,5-PeCB, and 2,3,7,8-TCDD proceeds through an epoxide intermediate, which is in good agreement with the previous experimental reports and consistent with our static density functional theory calculations. These results proved that our new tight-binding quantum chemical molecular dynamics method with first-principles parameterization is an effective tool to clarify the chemical reaction dynamics at reaction temperatures.