Extending \textit{ab initio} plasma-surface simulations to experimentally relevant scales.

The physical processes at the plasma-solid interface are extremely complex. They involve a huge number of elementary processes in the plasma, in the solid as well as charge, momentum and energy transfer across the interface. Even though the equations of motion for the participating charged and neutral particles are known, in principle, first principles quantum simulations are feasible only for extremely short times and/or small system sizes. If electronic quantum effects are not treated explicitly, one arrives at semi-classical molecular dynamics (MD) simulations that have become the main workhorse in plasma-surface simulations. Using microscopically founded force fields as an input, these MD simulations approach the quality of textit{ab initio} simulations in many cases. However, despite their simplified nature, these simulations require a time step that is of the order or below one femtosecond making it prohibitive to reach experimentally relevant scales of seconds or minutes and system sizes of micrometers. To bridge this gap in length and time scales without compromising the textit{ab initio} character and predictive power of the simulations, many acceleration strategies have been put forward in surface science. Examples include metadynamics, hyperdynamics, temperature accelerated dynamics, collective variable driven hyperdynamics and others. Recently we have presented two novel approaches: textit{Selective process acceleration} [Abraham textit{et al.}, J. Appl. Phys. textbf{119}, 185301 (2016)] and textit{Dynamical freeze out of dominant modes} [Filinov textit{et al.}, this issue]. In this article we give a brief overview on the different approaches and their underlying physical ideas, and we compare their strengths and weaknesses. Finally, we discuss their potential relevance for future plasma-surface simulations.