A detailed description of this procedure, justification of the methods used, and numerical results are available in the SI (Section 2). Unlike in the covalently bound molecules discussed above (polyenes and annulenes), the change in electronegativity of the helium clusters (He n ) is noticeable upon increasing cluster size. Therefore, Equation 11 is insufficient due to negligence of the change in χ. To account for that, let us reevaluate the solution. First, we examine the optimal charges of the fragments in Equation . The maximal value of the Q-independent term for the helium clusters can be estimated as (see Equations 28 and 29)