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

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. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Understanding the behavior of liquid ammonia is closely related to understanding the hydrogen bond networks in ammonia clusters. While ammonia clusters have received less attention compared to water clusters, insights can still be drawn from existing literature. By reviewing the structures, hydrogen bond networks, spectroscopy, and effects of temperature and solvent on ammonia clusters, as well as discussing their applications in determining solvation free energy and proton transfer free energy, we gain a better understanding of their potential applications and the need for future investigations.