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F ORCE F IELD O PTIMIZATION for F LUOROCARBON

F ORCE F IELD O PTIMIZATION for F LUOROCARBON. Seung Soon Jang. Optimization of van der Waals parameters of Fluorine. Exponential-6 function:. Tetrafluoromethane (CF 4 ). 1. Frequency (X.-G. Wang et al., J. Chem. Phys.112, 1353 (2000)).

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F ORCE F IELD O PTIMIZATION for F LUOROCARBON

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  1. FORCE FIELD OPTIMIZATIONforFLUOROCARBON Seung Soon Jang

  2. Optimization of van der Waals parameters of Fluorine Exponential-6 function: Tetrafluoromethane (CF4 ) 1. Frequency(X.-G. Wang et al., J. Chem. Phys.112, 1353 (2000)) 2. Crystal structure(A.N. Fitch et al., Z. Kristallogr. 203, 29 (1993)) Density=2.2249 g/cm3 (T=1.5 K) 3. Enthalpy of sublimation (A. Bondi, J. Chem. Eng. Data 8, 371 (1963), A. Eucken et al., J. Phys. Chem. 41B, 307 (1938)) Hsub=4.06 kcal/mol at 76 K 4. Isothermal compressibility(J. W. Stewart et al., J. Chem. Phys. 28, 425 (1958)) 5. Thermal expansion (D. N. Bol’Shutkin et al., Acta Cryst. B28, 3542 (1972))

  3. van der Waals Parameters for C and F a Experimental density @ T=1.5 K is 2.2249 g/cm3. b Experimental Hsub @ T=76 K is 4.06 kcal/mol.

  4. Isothermal Compressibility Compressibility curves were obtained by differentiating Murnaghan’s equation of state which were fitted to the each MD simulation result. Murnaghan’s equation of state where 0: compressibility at zero pressure V0: molar volume at zero pressure : an adjustable parameter The best fit for experimental result

  5. Thermal expansion The calculated thermal expansion is in good agreement with the experimental observation.

  6. Optimization of Valence Force Field Hessian-biased optimization method Expansion of energy of molecule The first derivative of energy: force on atom i-th component The second derivative of energy: Hessian . The mass-weighted Hessian: The vibrational eigenfunctions are obtained from the eigenvalue equation: If the experimental frequency set is available, we can replace theoretical frequency set by experimental one. The force field is determined to minimize the difference between HFF from force field and HQM&exp.

  7. Valence Force Field 1. Bond stretch Harmonic Kb R0 C-C 422.72451.5224 F-C 535.4583 1.3354 2. Valence angle bend Cosine harmonic K0 C-C-C 220.8724 120.0000 F-C-C 129.3900 120.0000 F-C-F 160.8744 120.0000 3. Dihedral angle torsion Dihedral Kd,n d n C-C-C-C 3.5464 1 3 F-C-C-C 3.5470 1 3 F-C-C-F 2.2211 -1 3

  8. Validation of Force Field Helical conformation of C6F14 • geometry Quantum mechanicsMolecular mechanics • 6-31G* & B3LYPNew Force Field • Clockwise f1 -165.0 -164.9 • helicity f2 -163.2 -163.2 • (trans minus) f3 -165.0 -164.9 • Counterclockwise f1 165.0 164.9 • helicity f2 163.2 163.2 • (trans plus) f3 165.0 164.9 RMS difference of atomic position: 0.0346 Å

  9. Trans plus Trans minus Validation of Force Field: Conformational Energy  Helical conformation and energy barrier between two energy minima were successfully reproduced.

  10. Validation of Force Field Density and Solubility Parameter of small fluorocarbons Reference data from database of Design Institute for Physical Property Data (DIPPR) Project 801, American Institute of Chemical Engineers (AIChE)

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