Study Of Lignite Structure By Molecular Dynamics Simulation And Quantum Chemistry

The application of computer molecular simulation techniques, which base on molecular mechanics, molecular dynamics and quantum chemistry, will more distinctly the coal macromolecular structure and quantify the structure parameters along with their reactivity from the view of modeling and simulating the coal three-dimensional structure.In this thesis, two chemical structural models were constructed based on several structure parameters derived from FTIR and 13C NMR data, which were processed by curve-fitting and curve-resolved. Modified models were obtained by simulation oftheir molecular vibration spectra using Cerius 4.6/IR module andthe structural parameters from 13C NMR. Potential energy, bondenergy and non-bond energy of the minimum-energy conformations of coal macromolecules were calculated by molecular mechanics calculation and molecular dynamics simulation. These results demonstrate the importance of hydrogen bonding and van der Waals (vdW) interactions in the formation and stabilization of coal macromolecular structure, and a strongest tendency of hydrogen bonding interactions to increase with the coal molecules but the Coulomb's force.ZINDO, a semi-empirical method of quantum chemistry implemented in programs Cerius2, was used to calculate and analyze the static conformation of models, formal charge of atoms, the bond length, HOMO and LUMO after running a preliminary minimization and other electronic properties also were studied. By analyzing bond length, all bonds including O, C=O in carbonyl group is the best stable, and R-O-R', C-O- Ar and C-O-R are the weakest bonds type. Fringe Cs tend to be oxygenized, which can be concluded from their atomic formal charge distributions. By analyzing HOMO and LUMO of all atoms, we find those carbon atoms that are located in where single bonds and double bondsalternate are not stable like those atoms located in conjuge aromatic systems, which can be used to predict the reaction locations of hydrogenation liquefaction and translate the role of catalysts during the processing in theory. Molecular models' UV/Vis also are calculated and analyzed in detail and the results sort well with the practice.