GOALI: Development of Transferable Force Fields for Phase Equilibria and Simulation Studies of Aggregation and Solvation in Microheterogeneous Fluids

内容提要：相平衡可传递力场的发展和微观非均相流体中聚集和溶解的模拟研究准确地了解复杂流体混合物的相平衡和其他热物理性质具有重要的基础和实际意义。分子模拟在预测热物理性质和提高我们对分子结构与宏观可观测性之间关系的理解方面的成功依赖于有效的模拟算法和准确的力场。这项研究的目标是发展三个水平的可转移力场和有偏蒙特卡罗方法。第一能级力场被称为Trappe-UA(相平衡联合原子的可转移势)，它使用联合原子表示烷基链段以及简单的Lennard-Jones和Coulombic项。在第二个层次，称为Trappe{EH(显式氢)，所有原子，包括烷基氢和某些酮对电子和键中心位置都被显式处理。在被称为Trappe-Poll(可极化)的第三级中，范德华相互作用和静电相互作用都可以对环境的变化做出反应。虽然第一级的设计是为了简单和计算效率高，具有良好的准确性，而第二级的目的是提高非极性或极性非氢键化合物的混合物的准确性。第三个级别仅针对尽可能高的准确度和可转移性。该项目将把TRAPPE-UA力场扩展到炔烃；烯烃氧化物；五元同芳环和杂芳环；卤代烃；初级、二级和三级氢氟醇、醚和氧化物；以及含硅和磷的官能团。Trappe-EH力场将扩展到环烷烃、烯烃和芳烃。Trappe-Pol力场的开发将继续使用水、烷烃、醇和乙醚的通用参数。除了力场开发，该项目还提出了相平衡第一性原理模拟的新模拟策略。使用可传递力场的分子模拟将被用作工程工具来预测各种体系的热物理性质，从而增加现有的实验数据库。这些模拟为复杂的化学体系提供了微观层面的信息，从而为分子结构和组成如何决定宏观现象提供了新的物理见解。特别是，将进行模拟以研究(I)均相成核现象，(Ii)含非离子表面活性剂的混合物中的界面性质、聚集和溶解度，以及(Iii)单体/齐聚物/聚合物体系中的相容性。拟议工作的更广泛影响包括开发可转移的力场、先进的算法和通过印刷出版物、网络界面和GNU通用公共许可证免费提供的软件包。这些工具是一个大型研究社区热切期待的。此外，拟议的项目将对各种教育、培训和辅导活动产生重大影响，并将允许继续开展外联活动。该项目将从一个紧密的大学-产业团队的广泛合作中进行项目，该团队由PI、两名研究生以及明尼苏达州圣保罗3M中央研究的罗斯和考德威尔博士组成。

ABSTRACTGOALI: Development of Transferable Force Fields for Phase Equilibriaand Simulation Studies of Aggregation and Solvationin Microheterogeneous FluidsAccurate knowledge of the phase equilibria and other thermophysical properties of complex fluidmixtures is of enormous fundamental and practical importance. The success of molecular simulation in predicting thermophysical properties and in advancing our understanding of the relationship between molecular architecture and macroscopic observable depends on the availability of efficient simulation algorithms and accurate force fields. The goals of the proposed research are to develop three levels of transferable force fields and of biased Monte Carlo methods. The first-level force field, called TraPPE-UA (transferable potentials for phase equilibria united atom), employs the united-atom representation for alkyl segments and simple Lennard-Jones and Coulombic terms. In the second level, called TraPPE{EH (explicit hydrogen), all atoms including alkyl group hydrogens and somelone-pair electron and bond-center sites are treated explicitly. In the third-level, called TraPPE-pol (polarizable), both the van der Waals and electrostatic interactions can respond to changes in the environment. Whereas the first level is designed for simplicity and computational efficiency with good accuracy, the second level is aimed at improved accuracy for mixtures of non-polar or a polar non-hydrogen-bonding compounds. The third level is directed solely at the highest possible level of accuracy and transferability. The project will extend the TraPPE-UA force field to alkynes; alkene oxides; 5-membered homo- and hetero-aromatic rings; halogenated hydrocarbons; primary, secondary, and tertiary hydrofluoro alcohols, ethers, and oxides; and silicon and phosphorous containing functionalities. The TraPPE-EH force field will be extended to cyclic alkanes, alkenes, and arenes. An the development of the TraPPE-pol force field will be continued with common parameters for water, alkanes, alcohols, and ethers.In addition to force field development, this project also addresses novel simulation strategiesfor first principles simulations of phase equilibria. Molecular simulations using the transferableforce fields will be employed as engineering tool to predict thermophysical properties of a variety of systems, thereby adding to the available experimental database. The simulations provide microscopic-level information for complex chemical systems, thereby giving new physical insight into how molecular architecture and composition determine macroscopic phenomena. In particular, simulations will be carried out to investigate (i) homogeneous nucleation phenomena, (ii) interfacial properties, aggregation, and solubilities in mixtures containing non-ionic surfactants, and (iii) miscibility in monomer/oligomer/polymer systems. The broader impacts of the proposed work include the development of transferable force fields, advanced algorithms, and software packages that are made freely available through print publications, a web interface, and GNU General Public Licenses. These tools are eagerly awaited by a large research community. Furthermore, the proposed project will have a major impact on various educational, training, and mentoring activities and will allow continued outreach. This project will project from extensive collaboration of a tight university-industry team consisting of the PI, two graduate students, and Drs. Ross and Caldwell of 3M Central Research, St. Paul, MN.