Nouranian S, Tschopp M A, Gwaltney S R, Baskes M I, Horstemeyer M F
Center for Advanced Vehicular Systems (CAVS), Mississippi State University, Mississippi State, MS 39762, USA.
Phys Chem Chem Phys. 2014 Apr 7;16(13):6233-49. doi: 10.1039/c4cp00027g.
In this work, we developed an interatomic potential for saturated hydrocarbons using the modified embedded-atom method (MEAM), a reactive semi-empirical many-body potential based on density functional theory and pair potentials. We parameterized the potential by fitting to a large experimental and first-principles (FP) database consisting of (1) bond distances, bond angles, and atomization energies at 0 K of a homologous series of alkanes and their select isomers from methane to n-octane, (2) the potential energy curves of H2, CH, and C2 diatomics, (3) the potential energy curves of hydrogen, methane, ethane, and propane dimers, i.e., (H2)2, (CH4)2, (C2H6)2, and (C3H8)2, respectively, and (4) pressure-volume-temperature (PVT) data of a dense high-pressure methane system with the density of 0.5534 g cc(-1). We compared the atomization energies and geometries of a range of linear alkanes, cycloalkanes, and free radicals calculated from the MEAM potential to those calculated by other commonly used reactive potentials for hydrocarbons, i.e., second-generation reactive empirical bond order (REBO) and reactive force field (ReaxFF). MEAM reproduced the experimental and/or FP data with accuracy comparable to or better than REBO or ReaxFF. The experimental PVT data for a relatively large series of methane, ethane, propane, and butane systems with different densities were predicted reasonably well by the MEAM potential. Although the MEAM formalism has been applied to atomic systems with predominantly metallic bonding in the past, the current work demonstrates the promising extension of the MEAM potential to covalently bonded molecular systems, specifically saturated hydrocarbons and saturated hydrocarbon-based polymers. The MEAM potential has already been parameterized for a large number of metallic unary, binary, ternary, carbide, nitride, and hydride systems, and extending it to saturated hydrocarbons provides a reliable and transferable potential for atomistic/molecular studies of complex material phenomena involving hydrocarbon-metal or polymer-metal interfaces, polymer-metal nanocomposites, fracture and failure in hydrocarbon-based polymers, etc. The latter is especially true since MEAM is a reactive potential that allows for dynamic bond formation and bond breaking during simulation. Our results show that MEAM predicts the energetics of two major chemical reactions for saturated hydrocarbons, i.e., breaking a C-C and a C-H bond, reasonably well. However, the current parameterization does not accurately reproduce the energetics and structures of unsaturated hydrocarbons and, therefore, should not be applied to such systems.
在本工作中，我们使用改进的嵌入原子方法（MEAM）开发了一种饱和烃的原子间势，这是一种基于密度泛函理论和对势的反应性半经验多体势。我们通过拟合一个大型实验和第一性原理（FP）数据库对该势进行参数化，该数据库包括：（1）从甲烷到正辛烷的一系列同系烷烃及其选定异构体在0 K时的键长、键角和原子化能；（2）H2、CH和C2双原子分子的势能曲线；（3）氢气、甲烷、乙烷和丙烷二聚体，即分别为(H2)2、(CH4)2、(C2H6)2和(C3H8)2的势能曲线；以及（4）密度为0.5534 g cc(-1)的致密高压甲烷系统的压力-体积-温度（PVT）数据。我们将根据MEAM势计算得到的一系列直链烷烃、环烷烃和自由基的原子化能和几何结构与通过其他常用的烃类反应势，即第二代反应性经验键序（REBO）和反应力场（ReaxFF）计算得到的结果进行了比较。MEAM再现实验和/或FP数据的精度与REBO或ReaxFF相当或更好。MEAM势对一系列具有不同密度的甲烷、乙烷、丙烷和丁烷系统的实验PVT数据预测得相当好。尽管MEAM形式主义过去已应用于主要具有金属键的原子系统，但当前工作表明MEAM势有望扩展到共价键合的分子系统，特别是饱和烃和基于饱和烃的聚合物。MEAM势已经针对大量金属单质、二元、三元、碳化物、氮化物和氢化物系统进行了参数化，将其扩展到饱和烃为涉及烃-金属或聚合物-金属界面、聚合物-金属纳米复合材料、基于烃的聚合物中的断裂和失效等复杂材料现象的原子/分子研究提供了一种可靠且可转移的势。尤其如此，因为MEAM是一种反应势，在模拟过程中允许动态键的形成和断裂。我们的结果表明，MEAM对饱和烃的两个主要化学反应，即断裂C-C键和C-H键的能量学预测得相当好。然而，当前的参数化不能准确再现不饱和烃的能量学和结构，因此，不应将其应用于此类系统
