Optimization of density functional tight-binding and classical reactive molecular dynamics for high-throughput simulations of carbon materials

Carbon materials and nanostructures (fullerenes, nanotubes) are promising building blocks of nanotechnology. Potential applications include optical and electronic devices, sensors, and nano-scale machines. The multiscale character of processes related to fabrication and physics of such materials requires using a combination of different approaches such as (a) classical dynamics, (b) direct Born-Oppenheimer dynamics, (c) quantum dynamics for electrons and (d) quantum dynamics for selected nuclei. We describe our effort on optimization of classical reactive molecular dynamics and density-functional tight binding method, which is a core method in our direct and quantum dynamics studies. We find that optimization is critical for efficient use of high-end machines. Choosing the optimal configuration for the numerical library and compilers can result in four-fold speedup of direct dynamics as compared with default programming environment. The integration algorithm and parallelization approach must also be tailored for the computing environment. The efficacy of possible choices is discussed.