Ammonia is stable and safe to handle, is combustible, and contains the largest fraction of hydrogen of any molecule except for pure hydrogen itself. These factors promise to make it a feasible alternative to the carbon-based energy carriers that are driving climate change. Research has begun to explore how ammonia could be used to directly power engines, gas turbines, and hydrogen fuel cells, for example. It is also believed that ammonia could be used to store energy for times when other renewables like wind and solar power cannot meet demand.

Much is known about ammonia, but this interest in using it as a fuel has initiated a search for new ammonia technologies. This has, in turn, led to an increased need among chemical engineers for accurate data describing ammonia's fundamental thermodynamic properties. Such properties include a wide variety of measurable traits such as phase equilibria, density, or heat capacity, for example, that characterize physical systems and determine how chemical processes work. In the case of ammonia, engineers would also like to have better knowledge of how such properties change when mixing ammonia with other molecules. Such knowledge could help them to optimize processes and operating conditions.

Dr. Jadran Vrabec, currently the director of the Institute for Process Sciences at the Technical University of Berlin, has spent much of his career using high-performance computing (HPC) to investigate thermodynamic properties at the molecular level. "Thermodynamic properties are 100% determined by molecular interactions," he explains. "And because these interactions happen so fast and at such a small scale, it is only possible to study them by performing large simulations using supercomputers."

In a recent paper published in the Journal of Chemical & Engineering Data, he and co-author Erich Mace of the TU Berlin report on the results of simulations focused on the thermodynamic properties of mixtures containing ammonia. Produced using the Hawk supercomputer at the High-Performance Computing Center Stuttgart (HLRS), their results add valuable data that could support the development of new applications of ammonia. The results could also help to assess the accuracy of other existing data, ensuring that engineers have the best available information for working with the substance.