Collaborative Research: CDS&E: ReaxFF2: Efficient and Scalable Methods for Long-time Reactive Molecular Dynamics Simulations

该项目旨在通过高效和可扩展的技术实现反应性分子系统的长时间模拟。长时间的反应模拟对于催化、电池界面、涉及水的生物模拟以及表面氧化和化学气相沉积（CVD）生长等一些科学问题至关重要。然而，这些方面的进展是有限的，因为使用现有方法进行大规模系统的长时间模拟非常困难，如果不是不可能的话。反作用力场（ReaxFF）方法在原则上非常适合于此目的。然而，当前ReaxFF模拟所需的短时间步长和计算昂贵的力场公式限制了ReaxFF的时间能力，以缩小模拟时间范围。这个项目旨在通过创建ReaxFF2来克服这些限制，ReaxFF2将把时间尺度延长一到两个数量级——从而使大规模的、长时间的RMD模拟可以被广泛的社区访问。制定的规范将向公众开放，该项目的成果将在一个专门的网站上突出显示，项目负责人也将把这些规范纳入讲习班。在创建ReaxFF2时，pi将显著增强Reax力场公式，并为可扩展模拟开发创新算法和软件实现。更具体地说，将制定替代ReaxFF相互作用，以消除能量方面的急剧导数，并将ReaxFF时间步长提高至少四倍。为了加速RMD所需的动态电荷分布模型，将开发迭代求解器的可扩展并行预处理技术。计算交互的任务并行方法、分层问题分解、关键核的矢量化以及混合精度算法的使用构成了将被用来充分利用大型计算机集群性能的主要技术。最后，将评估ReaxFF2方案中加速RMD概念的能力，并开发用于RMD的内联轨迹分析工具，以促进长期RMD模拟的研究。这个项目将显著地增强pi的软件开发、社区建设和RMD社区的维持工作。开发的代码、功能形式和参数集将公开可用，从而能够快速准确地对超出本项目范围的各种反应系统进行建模。在社区外展方面，这个项目的成果将在一个专门的网站上突出显示，这些成果也将被纳入pi的讲习班。该奖项由先进网络基础设施办公室颁发，由NSF数学和物理科学理事会的材料研究部门和化学部门联合支持。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project aims to enable long-time simulations of reactive molecular systems through efficientand scalable techniques. Long-time reactive simulations are critical for several scientific problemssuch as catalysis, battery interfaces, biological simulations involving water, and emergingareas like surface oxidation and chemical vapor deposition (CVD) growth. However, progress onthese fronts is limited because long-time simulations of large-scale systems are very difficult, ifnot impossible, to perform using existing methods. The Reactive Force Field (ReaxFF) method is in principle ideally suited for this purpose. However, the short time steps required in current ReaxFF simulations and the computationally expensive force field formulation limit ReaxFF's temporal capabilities to narrow simulation time ranges. This project aims to overcome such limitations by creating ReaxFF2,which will extend time scales by one to two orders of magnitude - thus making large-scale, long-time RMD simulations accessible to a wide community. Codes developed will be made publicly available and results from this project will be highlighted on a dedicated website, and they will also be incorporated into workshops by the PIs.In creating ReaxFF2, the PIs will enhance the Reax force field formulation significantly, and develop innovative algorithms and software implementations for scalable simulations. More specifically, alternative ReaxFF interactions will be formulated to eliminate sharp derivatives in energy terms and enhance ReaxFF time step lengths by at least a factor of four. To accelerate the dynamic charge distribution models needed in RMD, scalable parallel preconditioning techniques for the iterative solvers will be developed. A task parallel approach to compute interactions, hierarchical problem decomposition, vectorization of the key kernels, and use of mixed precision arithmetics constitutethe main techniques that will be utilized to fully leverage the performance capabilities of largecomputer clusters. Finally, capabilities of accelerated RMD concepts in the proposed ReaxFF2 formulation will be evaluated and inlined trajectory analysis tools for RMD will be developed to facilitate the study of long-time RMD simulations. This project will significantly enhance the PIs' software development, community building, and sustenance efforts for the RMD community. Codes, functional forms, and parameter sets developed will be made publicly available, enabling fast and accurate modeling of diverse reactive systems beyond the scope of this project. For community outreach, results from this project will be highlighted on a dedicated website, and they will also be incorporated into workshops by the PIs.This award by the Office of Advanced Cyberinfrastructure is jointly supported by the Division of Materials Research and the Division of Chemistry within the NSF Directorate for Mathematical and Physical Sciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.