A perspective on soft matter molecular simulations: Deformation and flow at mesoscopic timescales

In Multiscale Materials Modeling, an enduring vision is to extract the molecular mechanisms governing a certain materials phenomenon of interest in order to predict how the phenomenon will behave at a later time. This goal of predictive simulation has been discussed about a decade ago as a materials research challenge, in the Mesoscale Science Frontier, MSS. To date, it continues to motivate a growing community of computational materials science and technology. Here, we consider several materials phenomena of interest, each well known in their specific areas of application, to note that while molecular dynamics simulation is arguably the most widely used method, MD results have limitations in predicting or explaining the behavior of the phenomenon. For the type of phenomena selected here, we believe that one can raise the issue of whether MD is an appropriate method of molecular simulation in the design and performance testing of complex materials. There exists an alternative to MD, the approach of meta-dynamics simulation based on energy landscape sampling and transition state theory. This approach is notable because it allows predictive molecular simulations over timescales considerably longer than the traditional MD. We are in the process of implementing an enhanced meta-dynamics approach aimed at identifying unknown defect mechanisms, making it particularly well-suited for investigating the deformation processes in engineering alloys at timescales relevant to laboratory measurements of component performance and durability assurance. Our motivation is that such simulation capabilities will find many materials-centric applications. One such application is known as plasma-materials interactions, PMI. In PMI, the phenomenon of nuclear irradiation damage has been a practical challenge, relevant to both nuclear fission and fusion power generation systems. For the present perspective, we will focus on the use of meta-dynamics simulations in collaboration with the research activities at an academic fusion research center.