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Derivation of fluorine and hydrogen atom parameters using liquid simulations
Author(s) -
Gough Craig A.,
Debolt Stephen E.,
Kollman Peter A.
Publication year - 1992
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540130806
Subject(s) - fluorine , chemistry , van der waals force , hydrogen , propane , enthalpy , hydrocarbon , thermodynamics , enthalpy of vaporization , van der waals radius , butane , vaporization , hydrogen atom , carbon fibers , molar volume , hydrogen fluoride , molecule , organic chemistry , materials science , catalysis , physics , alkyl , composite number , composite material
Simulations of periodic boxes of tetrafluoromethane and trifluoromethane were run to determine van der Waals parameters for fluorine and for hydrogen attached to a fluorine‐bearing carbon. The simulations of CF 4 were performed first to determine the optimal van der Waals radius R * and well depth ε for fluorine by adjusting these parameters to reproduce the experimental molar volume and enthalpy of vaporization of CF 4 . The best values of R * and ε were determined to be 1.75 Å and 0.061 kcal/mol. Using these fluorine parameters, the simulations of CHF 3 were then performed to determine if the hydrogen of this molecule required a smaller R * than that used for the “normal” hydrocarbon hydrogen determined by Spellmeyer and Kollman (results in preparation). That R * was determined by running Monte Carlo simulations on methane, ethane, propane, and butane and adjusting R * and ε for carbon and hydrogen to reproduce the experimental molar volume and enthalpy of vaporization. It was found that an R ε of 1.21 Å was optimal, significantly smaller than the R * = 1.49 Å found by Spellmeyer for “normal” hydrocarbon hydrogens. This value of R * is in good agreement with the R * for the hydrogen in CHF 3 derived independently using ab initio calculations and molecular mechanics on F 3 C H … OH 2 by Veenstra et al. © 1992 by John Wiley & Sons, Inc.