Quantum Chemistry Method to Calculate Intermolecular Interactions and Molecular Dynamics Simulations of Trifluoromethane
Date Issued
2010
Date
2010
Author(s)
Chung, Yi-Hsing
Abstract
The global warming due to the greenhouse effect is one of the most important issues in earth. Not only carbon dioxide affects global warming, but also hydrofluorocarbons affect global warming. The research discovered hydrofluorocarbons affect global warning more than carbon dioxide. Therefore we have interest in hydrofluorocarbons. Trifluoromethane is a tetrahedron structure of hydrofluorocarbons, and its Global Warming Potential is 12,000 times more than carbon dioxide. So we start to study trifluoromethane. Quantum chemistry calculations use three methods, HF and MP2 and DFT. HF and MP2 use 11 basis sets, and DFT uses 80 exchange-correlation function to compare to our computation with MP2. All of the computations add BSSE correct. Then we use MP2/aug-cc-pVQZ to do the monomer optimization of trifluoromethane, and choose 14 conformers (A~N). We use 5 site Lennard-Jones potential model with coulomb potential in our fitting to quantum chemistry calculated data. Then construct force field with there parameters. We also take the parameters into our molecular dynamics simulations. We simulate radial distribution function and velocity correlation function. Also, We simulate velocity correlation function along the gasification curve of trifluoromethane phase diagram. And we integrate velocity correlation function to obtain diffusion constant and simulate diffusion constant with different temperature and different density. The simulation results are in good agreement with experiment data. It shows that using quantum chemistry calculations to construct force field, and to do molecular dynamics simulation can yield good result.
Subjects
Trifluoromethane
Hatree-Fock (HF) approximation
M?ller-Plesset (MP) perturbation theory
Density Function Theory(DFT)
Radial distribution function(RDF)
Velocity autocorrelation function(VAF)
Molecular Dynamics Simulations
Gaussian 03 package
Type
thesis
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