Systematic investigation of the molecular behavior of C50X2 (X???=???H,F): An echo of the H/F parallels on structures and energetics among their derivativesElectronic supplementary information (ESI) available: Heats of formation, ionization potential (IP), electron affinity (EA) and the HOMO???LUMO energy gap for all possible isomers of C50X2 (X???=???H,F); the results of POAV analysis for several prototypical C50F2 isomers; electronic absorption spectra. See http://www.rsc.org/suppdata/cp/b2/b206653j/