Molecular dynamics simulation of perfluorohexanone-based synergistic gas mixtures and mechanistic prediction of hydrogen fluoride formation pathways.

CONTEXT: Perfluorohexanone (C6F12O, Novec 1230) has emerged as a leading halon alternative for fire suppression due to its near-zero ozone depletion potential and short atmospheric lifetime, yet its high-temperature decomposition can generate hydrogen fluoride (HF), posing secondary damage risks to protected assets-particularly in enclosed spaces housing cultural heritage artifacts where corrosive gas exposure must be minimized. Although the qualitative effects of inert dilution and an additional fluorinated component can be anticipated, formulation design requires quantitative information on the magnitude, timing, and nonlinearity of C6F12O conversion and HF-species formation across temperature, initial-density, and blend-ratio conditions. The present simulations were therefore designed as a controlled molecular-level comparison to identify formulations and conditions that warrant subsequent fire-suppression and HF-emission testing. Elevated temperature consistently accelerated C6F12O conversion and increased HF-species accumulation. N₂ substitution reduced the absolute number of identified HF species but delayed C6F12O conversion, whereas C3HF7 blending did not provide a consistent HF-reduction advantage at elevated temperatures. Among the investigated N2 blending ratios, the C6F12O: N2 = 1:3 system showed the lowest HF-species response and was therefore identified as a candidate for subsequent HF-mitigation testing rather than as an established optimum for fire-extinguishing operation. METHODS: This work employs a published ReaxFF parameterization to conduct reactive molecular dynamics simulations of the investigated C-H-O-F systems across the selected temperature, fixed-volume initial-density, and blend-ratio conditions. Three series of simulations were performed: (i) pure C6F12O as the baseline reference, (ii) C6F12O blended with N₂ to quantify the system-level effect of inert substitution, and (iii) C6F12O blended with C3HF7 to examine the effect of a reactive hydrogen- and fluorine-containing partner. Across the study, five temperatures (1400-3000 K) and several fixed-volume density conditions corresponding to nominal initial-pressure labels of 0.1-0.3 MPa were examined; multiple blend ratios were additionally considered for the N2- and C3HF7-containing systems. The temporal evolution of intact perfluorohexanone, representative fragment populations, and identified HF species was compared across the investigated conditions to distinguish parent-molecule conversion from subsequent fluorine redistribution and HF formation.