DERIVATION OF CLASS-II FORCE-FIELDS .1. METHODOLOGY AND QUANTUM FORCE-FIELD FOR THE ALKYL FUNCTIONAL-GROUP AND ALKANE MOLECULES
DERIVATION OF CLASS-II FORCE-FIELDS .1. METHODOLOGY AND QUANTUM FORCE-FIELD FOR THE ALKYL FUNCTIONAL-GROUP AND ALKANE MOLECULES
复制标题
DOI：
10.1002/jcc.540150207
复制
发表时间：
1994-02-01
影响因子：
3
通讯作者：
HAGLER, AT
中科院分区：
文献类型：
--
作者：
MAPLE, JR;HWANG, MJ;HAGLER, AT
提出了一种计算分子模拟力场的新方法。它是基于从头算势能面解析表示的推导和参数化。本文给出了推导烷烃量子力学力场（QMFF）的一般方法。它是基于16种代表性烷烃的能面采样。对于碳氢化合物，该力场包含66个力常数和参考值。它们适合于描述能量表面的128,376个量子力学能量和能量导数。给出了解析力场表达式的详细形式和各结果参数的取值。然后进行了一系列计算，以测试该力场在能量方面重现从头算能量面特征的能力，以及能量对分子变形的一阶和二阶导数。结果表明，拟合良好，所有分子的均方根能量偏差小于7%。此外，虽然只使用了两种原子类型，力场解释了高应变物种的性质，如环丙烷和甲基环丙烷，以及非应变系统。量子能量表面所包含的信息表明它是明显的非调和的，并且分子内部之间存在重要的耦合相互作用。这些相互作用的性质的表示，不存在于对角线，二次力场（I类力场），被证明是重要的准确计算分子的能量表面。从量子能量面导出的第二类力场的特征是考虑到这些重要的分子内力。还评估了势能函数中每个相互作用项的重要性。键非调和性、角非调和性、键/角、键/扭、角/角/扭交叉项相互作用导致扭曲结构能量和能量导数的最显著的整体改善。讨论了每个能量项对先进力场发展的影响。最后，本文介绍的探索量子能量表面的技术可以用来确定力场的可转移程度和有效范围。后者对于在新环境中推导用于分子力学和分子动力学计算的广泛分子（通常含有官能团）的力场是至关重要的。(C) 1994, John Wiley and Sons, Inc。
A new method for deriving force fields for molecular simulations has been developed. It is based on the derivation and parameterization of analytic representations of the ab initio potential energy surfaces. The general method is presented here and used to derive a quantum mechanical force field (QMFF) for alkanes. It is based on sampling the energy surfaces of 16 representative alkane species. For hydrocarbons, this force field contains 66 force constants and reference values. These were fit to 128,376 quantum mechanical energies and energy derivatives describing the energy surface. The detailed form of the analytic force field expression and the values of all resulting parameters are given. A series of computations is then performed to test the ability of this force field to reproduce the features of the ab initio energy surface in terms of energies as well as the first and second derivatives of the energies with respect to molecular deformations. The fit is shown to be good, with rms energy deviations of less than 7% for all molecules. Also, although only two atom types are employed, the force field accounts for the properties of both highly strained species, such as cyclopropane and methylcyclopropanes, as well as unstrained systems. The information contained in the quantum energy surface indicates that it is significantly anharmonic and that important intramolecular coupling interactions exist between internals. The representation of the nature of these interactions, not present in diagonal, quadratic force fields (Class I force fields), is shown to be important in accounting accurately for molecular energy surfaces. The Class II force field derived from the quantum energy surface is characterized by accounting for these important intramolecular forces. The importance of each of the interaction terms of the potential energy function has also been assessed. Bond anharmonicity, angle anharmonicity, and bond/angle, bond/ torsion, and angle/angle/torsion cross-term interactions result in the most significant overall improvement in distorted structure energies and energy derivatives. The implications of each energy term for the development of advanced force fields is discussed. Finally, it is shown that the techniques introduced here for exploring the quantum energy surface can be used to determine the extent of transferability and range of validity of the force field. The latter is of crucial importance in meeting the objective of deriving a force field for use in molecular mechanics and dynamics calculations of a wide range of molecules often containing functional groups in novel environments. (C) 1994 by John Wiley and Sons, Inc.