Topologies of hydrogen-bond networks: Amorphous Ammonia Dihydrate

Ammonia and water are the two most ubiquitous hydrogen-bonded substances, being widespread both on Earth and in extraterrestrial planetary environments such as the Titan, the satellite of Saturn. Understanding their behaviour is crucial both from a fundamental point of view, as the simplest H-bonded binary mixture as well as from a practical one, being the most readily available general-use solvents in chemical manufacturing. Despite their importance and the central place they occupy in physical, chemical and material science, the water-ammonia mixtures are still not fully understood. Part of the difficulty consists in them easily forming amorphous solids not crystalline ones when cooled, whose structures are yet unknown. In this proposal we would like to determine the structure of the ambient pressure amorphous phase and so elucidate the mechanism behind H-bonding in ammonia-water.