AMBER-ii: New Combining Rules and Force Field for Perfluoroalkanes

A molecular mechanics force field of the AMBER/OPLS family for perfluoroalkanes, noble gases, and their mixtures with alkanes has been proposed. We had to abandon the traditional Lorentz–Berthelot combining rules for the Lennard-Jones potential to be able to uniformly describe these substance classes and their mixtures. Instead, the Waldman-Hagler rules developed for noble gases were used for all of these elements except hydrogen. Hydrogen is considered to be a particular substance to which the usual Lorentz–Berthelot rules are applied. The proposed rules have little effect on the organic chemistry of H, C, N, and O elements but make it compliant with the chemistry of heavy elements. Because of assigning a relatively high partial charge of −0.37e to fluorine atoms, the new force field reproduces the mutual insolubility of higher liquid alkanes and perfluoroalkanes.本研究提出了适用于全氟烷烃、稀有气体及其与烷烃混合物的 AMBER/OPLS 家族分子力学力场。鉴于需统一描述这些物质类别及其混合物，我们不得不摒弃传统的 Lorentz-Berthelot 结合规则以适用于 Lennard-Jones 势。因此，我们采用了专为稀有气体开发的 Waldman-Hagler 规则，适用于除氢以外的所有这些元素。氢被认为是一种特殊的物质，对其适用常规的 Lorentz-Berthelot 规则。所提出的规则对 H、C、N 和 O 元素的有机化学影响微乎其微，但使得力场与重元素化学相吻合。由于对氟原子赋予相对较高的部分电荷（-0.37e），新的力场能够再现高液态烷烃与全氟烷烃的互溶性。