Hydrogen bond networks of ammonia clusters: What we know and what we don’t know

Abstract Understanding the behaviour of liquid ammonia is subjected to understanding the hydrogen bond networks in ammonia clusters as well as their interactions. In comparison to water clusters, hydrogen bond networks of ammonia clusters have received less attention. Nevertheless, from the available literature, one can draw some understanding of the hydrogen bond networks in ammonia clusters. In this work, we reviewed what we know on ammonia clusters regarding their structures and hydrogen bond networks, their spectroscopy, the temperature and solvent effects on the stability of their structures as well as on their hydrogen bond networks. In addition, we have also discussed the application of the ammonia clusters to determine the solvation free energy and enthalpy of the proton in ammonia. Besides, their application to the determination of the proton transfer free energy from water to ammonia has been also discussed. As part of what we don’t know, we presented some perspectives for future investigations on ammonia clusters as well as their potential application in understanding some processes.