Coarse Grained Molecular Mechanics/Molecular Dynamics Force Field For Hydrocarbon In Petroleum Chemistry

With the development of computer science, quantum mechanics is widely used inresearch simulation. As a result, computer hardware is meeting more demanding need fromresearchers. In order to improve calculation efficiency, a kind of method is developed basingon classic mechanics called non-quantum simulation which is composed of molecularmechanics and molecular dynamics. In recent years, coarse grained simulation methodobtained great development due to its high calculation efficiency. During the simulationprocess, this method can simplify molecular structure, thus the calculation number offreedom degree is reduced. Coarse-grained molecular mechanics/molecular dynamicssimulation need specific force field to complete, however, there’s no general force field atpresent. In order to solve this problem, coarse-grained model is applied in this paper toconstruct coarse-grained molecular mechanics/molecular dynamics force field in hydrocarbonfractions of petroleum.In molecular dynamics simulation, we first use Newton motion equation to get theposition coordinates and momentum of each particle; then we use statistical calculationmethod to get the dynamic characteristics of the system, thus we can get the macroscopicproperties of the system. In this paper, MS Forcite and MS Mesocite were applied to domolecular dynamics simulation. Taking consideration of the periodic boundary conditions,the Verlet algorithm was applied to the Newtonian equation integral.In this paper, we classified the petroleum hydrocarbons into four kinds: alkanes, olefin,aromatic and naphthenic hydrocarbons, counted the common hydrocarbon molecularstructure in petroleum fractions, and constructed the fewest coarse-grained force field tocover the whole hydrocarbon fractions of the coarse grained structure unit. Regard of different coarse-grained models, we found a similar compound model to do all-atommolecular mechanics/molecular dynamics simulation. After we got corresponding radicaldistribution functions, we used the Boltzmann inversion scheme to obtain the correspondingforce field parameters.Constructed coarse-grained force field was applied for coarse grained molecularmechanics/molecular dynamics simulation, and coarse graining system density, free energyof mixing and other related thermodynamic parameters were calculated. After all the workwas done, we found that coarse graining simulation values was equal to experimentalvalues and the all-atom simulation values, which proves the accuary of hydrocarboncompound coarse-grained force field we constructed in this paper.