Adiabatic electron affinities of small superhalogens: LiF2, LiCl2, NaF2, and NaCl2

Abstract

Geometries and frequencies for the neutral MX 2 and ionic MX 2 Ϫ species ͑MϭLi, Na, and XϭF, Cl͒ are studied by several theoretical methods: density functional theory ͑Becke-3-Lee-Yang-Parr͒ ͓DFT͑B3LYP͔͒, second-order many-body perturbation theory ͓MBPT͑2͔͒, and coupled-cluster with singles and doubles ͑CCSD͒. The geometries optimized at the CCSD/6-311ϩG͑d͒ level are used in CCSD͑T͒ calculations with a large atomic natural orbital basis to compute adiabatic electron affinities (EA ad ), which are found for LiF 2 , LiCl 2 , NaF 2 , and NaCl 2 to be 5.45, 4.97, 5.12, and 4.69 eV, respectively. The highest EAs among all the atoms of the periodic table occur in the halogen atoms ͑fluorine, 3.40 eV; chlorine, 3.62 eV͒; therefore all four of these triatomic radicals are properly termed superhalogens. LiF 2 , LiCl 2 , NaF 2 , and NaCl 2 are thermodynamically stable, and their dissociation energies computed at the CCSD with the noniterative inclusion of triples ͓CCSD͑T͔͒ level are 20.5, 24.9, 19.3, and 25.2 kcal/mol, respectively. LiF 2 Ϫ , LiCl 2 Ϫ , NaF 2 Ϫ , and NaCl 2Ϫ are more stable than their neutral parents with CCSD͑T͒ dissociation energies of 69.5, 58.7, 49.0, and 52.5 kcal/mol, respectively. The computed vertical electron detachment energies of LiF 2 Ϫ , LiCl 2Ϫ , NaF 2 Ϫ , and NaCl 2 Ϫ are 6.51, 5.88, 6.18, and 5.77 eV, respectively, which are in nice agreement with the values calculated by Scheller and Cederbaum by the Green-Function method.

Negative ion mode electrospray ionization mass spectrometry study of ammonium-counter ion clusters

“…These values are reasonable for ions held together by electrostatic interactions. According to Gutsev°et°al.° [18],°CID°of°NaCl 2 Ϫ to Cl Ϫ takes 2.28 eV, similar to that found for the more stable ions studied in the present°work.°Figures°7°and°8°show°that°the°instrument can distinguish the CID threshold energies for the various ions, although there could be a systematic error …”

“…The results from the threshold measurement for the dissociation of NaCl 2 Ϫ gave a threshold energy of 1.65 eV (center of mass, data not shown). This measured value is 0.63 eV lower than the°computational°value°of°2.277°eV° [18].°This°offset value is similar to the 0.76 eV offset obtained from the previous NO 3 Ϫ threshold°measurement° [13]°and°con-firms that the offset is not strongly dependent on the ion selected. We are more confident in the experimentallymeasured thermochemical data used previously, so 0.76 eV has been added to all the voltage thresholds reported below to generate "corrected" thresholds.…”

Structure and properties of the aluminum borates Al(BO2)n and Al(BO2)n−, (n = 1–4)

“…Superhalogens with polyvalent ligands are described by the formula [10] MX k/mþ1 where k is the maximal formal valence of M and m is the normal valence of X that factors m, for example, ClO 4 or PO 3 . No exception to the superhalogen formula was found in studies of halogen-containing superhalogens MX 2 (M ¼ Li, Na; X ¼ Cl, Br, I), [11][12][13] MX 3 (M ¼ Be, Mg, Ca; X ¼ Cl, Br), [14][15][16] OF 3 , [17] MX 4 (M ¼ B, Al; X ¼ F, Cl, Br), [18][19][20] SiF 5 , [21] SiCl 5 , [22] GeF 5 , [23] PF 6 , [24] and PCl 6 . [25] The oxygen-containing superhalogens possess generally smaller electron affinities than the halogen-containing superhalogens, which can be related with the smaller EA of 1.461 eV [8] of oxygen atom.…”

First principle study of CrF n (n = 1–7) nano clusters: An investigation of superhalogen properties

“…According to this formula, LiF 2 should be a superhalogen and indeed its EA of 5.45 eV [4] is larger than that of F. Wang et al [5] reported a combined photoelectron spectroscopic and theoretical study of six superhalogen anions, MX 2 -(M = Li and Na; X = Cl, Br and I). They also tried to perform experiments on the corresponding fluoride superhalogens, LiF 2 -and NaF 2 -.…”