title: Structures, vibrational frequencies, and stabilities of halogen cluster anions and cations, X(n)(+/-), n = 3, 4, and 5.
abstract: The structures, vibrational frequencies, and thermodynamic stabilities of the homonuclear polyhalogen ions, X3(+), X3(-), X4(+), X4(-), X5(+), and X5(-) (X = Cl, Br, I), have been calculated at the CCSD(T) level. The energetics were calculated using the Feller-Peterson-Dixon approach for the prediction of reliable enthalpies of formation. The calculations allow the following predictions where stabilities are defined in terms of thermodynamic quantities. (1) The X3(+) cations are stable toward loss of X2; (2) the X3(-) anions are marginally stable toward loss of X2 with Cl3(-) being the least stable; (3) the X4(+) cations and X4(-) anions are only weakly bound dimers of X2(+1/2) and X2(-1/2) units, respectively, but the cations are marginally stable toward decomposition to X3(+) and X, with I4(+) having the lowest dissociation energy, whereas the X4(-) anions decompose spontaneously to X3(-) and X; (4) the X5(+) cations are only marginally stable at low temperatures toward loss of X2, with Cl5(+) being the least stable; and (5) the X5(-) anions are also only stable at low temperatures toward loss of X2, with Cl5(-) being the least stable.
authors.affiliation: Department of Chemistry, The University of Alabama , Shelby Hall, Box 870336, Tuscaloosa, Alabama 35487-0336, United States.
authors.forename: K Sahan
authors.initials: KS
authors.lastname: Thanthiriwatte
authors.forename: Jason M
authors.initials: JM
authors.lastname: Spruell
authors.forename: David A
authors.initials: DA
authors.lastname: Dixon
authors.forename: Karl O
authors.initials: KO
authors.lastname: Christe
authors.forename: H Donald B
authors.initials: HD
authors.lastname: Jenkins