Theoretical investigation on structural properties of ethylene clusters (C2H4)n (n ⩽ 25)

► Optimal geometries of ethylene clusters (C2H4)n in the range of n ⩽ 25. ► The heuristic optimization method combined with geometrical perturbations. ► Intermolecular distances and rotational constants are used to examine the structures. ► The ethylene clusters take no icosahedral motif. ► The structural evolution of the ethylene clusters is complicated.