A density functional theory for symmetric radical cations from bonding to dissociation

Ester Livshits, Roi Baer*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


It has been known for quite some time that approximate density functional (ADF) theories fail disastrously when describing the dissociative symmetric radical cations R2+. By considering this dissociation limit, previous work has shown that Hartree-Fock (HF) theory favors the R +1-R0 charge distribution, whereas DF approximations favor the R+0.5-R+0.5. Yet, general quantum mechanical principles indicate that both these (as well as all intermediate) average charge distributions are asymptotically energy degenerate. Thus, HF and ADF theories mistakenly break the symmetry but in a contradicting way. In this letter, we show how to construct system-dependent long-range corrected (LC) density functionals that can successfully treat this class of molecules, avoiding the spurious symmetry breaking. Examples and comparisons to experimental data is given for R = H, He, and Ne, and it is shown that the new LC theory improves considerably the theoretical description of the R2+ bond properties, the long-range form of the asymptotic potential curve, and the atomic polarizability. The broader impact of this finding is discussed as well, and it is argued that the widespread semiempirical approach which advocates treating the LC parameter as a system-independent parameter is in fact inappropriate under general circumstances.

Original languageAmerican English
Pages (from-to)12789-12791
Number of pages3
JournalJournal of Physical Chemistry A
Issue number50
StatePublished - 18 Dec 2008


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