Molecular Model Construction of Low-Quality Coal and Molecular Simulation of Chemical Bond Energy Combined with Materials Studio

Molecular simulations, which can explain macroscopic phenomena from a microscopic molecular perspective, are currently receiving considerable attention. The key to this is how to characterize molecular structural parameters and construct realistic numerical models of molecules. In this paper, 13C NMR tests were performed on ten coal samples, the macromolecular carbon skeleton structure of different coal samples was calculated and analyzed, and the macromolecular structure model of coal was constructed and modified using Materials Studio (MS). According to the principles of molecular mechanics and molecular dynamics, the energy stabilization model of coal macromolecular structure was geometrically optimized. Also, based on the quantum chemical calculations, the bond lengths and other parameters of the molecular structure model were obtained. Finally, combined with the fragmentation of chemical bonds after breaking, the main reactive groups in coal and the types of free radicals generated were summarized. The results show that the coal metamorphism degree is positively correlated with aliphatic structure stability. The constructed molecular model of coal has a reasonably good fit after correction by comparing the experimental spectra. The molecular structure model after energy optimization has a strong spatial three-dimensionality and lower total molecular energy. The molecular structure we built is more stable and closer to that of real coal samples. The more branched C–C bonds have longer bond lengths and lower bond energies. In addition, the breakage of C–C reactive chemical bonds in coal molecules results in the formation of a number of different types of reactive radicals, which in turn lead to the formation of gases such as carbon monoxide and carbon dioxide. This work has the potential to be applied to investigate the microscopic properties of the initial active chemical bond breakage behind macroscopic phenomena such as coal powder explosion or combustion.