ENHANCING COMBUSTION HEAT CALCULATIONS OF PHOSPHORUS-CONTAINING FLAME RETARDANTS: COMBINING GFN2-XTB EFFICIENCY WITH DFT/B3LYP ACCURACY THROUGH ADJUSTMENT FACTORS

The heat of combustion for phosphorus-containing compounds was investigated using two widely employed computational methods: the self-consistent tight-binding quantum chemical method (GFN2-xTB) and density functional theory (DFT) at the B3LYP/6-311G(d,p) level. Both methods were applied to optimize the molecular structures and calculate the vibrational frequencies of a series of standard samples, including alkanes, aldehydes, alcohols, and arenes, to benchmark their performance. The results indicated that DFT/B3LYP, as expected, provided more accurate predictions of the combustion heat compared to GFN2-xTB. However, one of the key advantages of GFN2-xTB is its significantly shorter computational time, which is especially useful for large systems where computational efficiency is critical. In addition, a consistent pattern of deviation ratios between the two methods was observed specifically for phosphorus-containing compounds. This consistency allowed for the derivation of adjustment factors, which were used to calibrate the GFN2-xTB results for the combustion reactions of specific phosphorus-based flame retardants, such as bis(diphenyl phosphate) and bisphenol A bis(diphenyl phosphate). By applying these adjustment factors, the computational efficiency of GFN2-xTB could be preserved, while still benefiting from the high accuracy of DFT/B3LYP. This approach offers a balanced solution for studying complex combustion processes, particularly those involving large and intricate molecules. It enables rapid analysis of larger systems without sacrificing the precision required for understanding detailed chemical reactions. The method has the potential to streamline the study of combustion in materials science, environmental chemistry, and the development of advanced flame retardants. For citation: Nguyen Huu Hieu, Nguyen Ngoc Ha, Nguyen Thi Thu Ha enhancing combustion heat calculations of phosphorus-containing flame retardants: combining GFN2-xTB efficiency with DFT/B3LYP accuracy through adjustment factors. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 7. P. 65-73. DOI: 10.6060/ivkkt.20256807.7184.