Previous work on ammonium bisulfate clusters found that hydrogen bonding and salt bridge formation were crucial interaction forces at play in stabilizing these clusters against evaporation and for further growth into larger sizes. However, comparing isomers B and C to the experimentally present isomer A exemplifies that for this type of cluster, hydrogen bonding might not be the most important force at play. Structurally, in the higher energy isomers, B and C, there are four hydrogen bonds, whereas in the experimentally present isomer A, there are only three hydrogen bonds. Looking closely at the structure of isomer A, we see that the iodine of the free OH iodic acid and the non-hydrogen bonded oxygen of the other iodic acid molecule appear to be oriented in a way where a halogen bonding interaction could optimally take place (shown as a green dashed line in Figure ). Both halogen and hydrogen bonding have previously been found to be important in iodic acid -methanesulfonic clusters explored via ACDC. Yet, this finding for the (1, 2, 0) cluster suggests that halogen bonding may outcompete hydrogen bonding in terms of stabilizing this cluster experimentally.