The conclusion of this examination of cluster structures and energetics is how important a triple bond is for the features of weakinteraction.The interaction among the local quadrupoles of the triple bonds, either in HCCH or HCN, is significant. The sizable dipole of HCN relative to the zero dipole of acetylene has some effect on acetylene clusters to which it is attached,
but in certain ways, the effect is small or latter only for HCN–HCCH pairs. A consistent qualitative result of these calculations is that HCN being a replacement for an acetylene in a pure cluster leads to fairly small structural changes. This is especially clear for the pentamer. In Fig. 2a ghost image of ðHCCHÞ5 is included with the