Photoelectron spectra and structure of the Mnn(-) anions (n = 2-16).

Photoelectron spectra of the Mnn(-) anion clusters (n = 2-16) are obtained by anion photoelectron spectroscopy. The electronic and geometrical structures of the anions are computed using density functional theory with generalized gradient approximation and a basis set of triple-ζ quality. The electronic and geometrical structures of the neutral Mnn clusters have also been computed to estimate the adiabatic electron affinities. The average absolute difference between the computed and experimental vertical detachment energies of an extra electron is about 0.2 eV. Beginning with n = 6, all lowest total energy states of the Mnn(-) anions are ferrimagnetic with the spin multiplicities which do not exceed 8. The computed ionization energies of the neutral Mnn clusters are in good agreement with previously obtained experimental data. According to the results of our computations, the binding energies of Mn atoms are nearly independent on the cluster charge for n > 6 and possess prominent peaks at Mn13 and Mn13(-) in the neutral and anionic series, respectively. The density of states obtained from the results of our computations for the Mnn(-) anion clusters show the metallic character of the anion electronic structures.

Structure and Properties of Polyfluoride Fn(-) Clusters (n = 3-29).

The electronic and geometrical structures of the neutral Fn and singly negatively charged Fn(-) polyfluorides (n = 3-29) are studied using three levels of theory: density functional theory (DFT) with generalized gradient approximation, hybrid Hartree-Fock-DFT, and hybrid HF-DFT with long-range corrections. For n > 4, each polyfluoride possesses a number of states with different geometries that are closely spaced in total energy. The geometrical structures of the lowest total energy states follow different patterns for the even-n and odd-n Fn(-) anion branches with a preference for higher symmetry geometries. The largest F29(-) anion considered is found to possess Oh symmetry. All the anions beginning with F3(-) are found to possess adiabatic and vertical electron detachment energies exceeding the electron affinities of halogen atoms and are therefore superhalogen anions. Electron affinities, energies of formation, and binding energies show oscillatory behavior as functions of the number n of fluorine atoms. The neutral Fn species are found to be barely stable and are bound by polarization forces. The Fn(-) anions, on the contrary, are quite stable toward the loss of F, F(-), and F2(-), but not to the loss of F2.

Structure and properties of Fe(n), Fe(n)-, and Fe(n)+ clusters, n = 7-20.

The electronic and geometrical structures of the Fe(n), Fe(n)(­), and Fe(n)(+) series (n = 7­20) are studied using all-electron density functional theory with the generalized gradient approximation. Equilibria of the geometrical configurations of the lowest total energy states in all three series are found to be similar except for Fe(9)(­), Fe(9)(+), Fe(10)(­), Fe(10)(+), Fe(15)(­), and Fe(19)(+). Our computed ionization energies of the neutrals, vertical electron detachment energies, and energies of Fe atom abstraction are in good agreement with experiment. It is found that the one-electron model corresponding to the change in the total magnetic moment of ±1.0µ(B) due to either attachment or detachment of an electron is valid in most cases. The exceptions are Fe(4)(+), Fe(10)(­), Fe(10)(+), Fe(12)(­), Fe(13)(+), and Fe(14)(+), where the change in the total magnetic moment is +3µ(B) (Fe(10)(­) and Fe(12)(­)), −3µ(B) (Fe(4)(+), Fe(11)(+), and Fe(14)(+)), and −9µ(B) (Fe(13)(+)). The reason for an anomalously large quenching of the total spin magnetic moment in Fe(13)(+) is explained. Our computed total spin magnetic moments per atom match the recent experimental values within the experimental uncertainty bars.

Density functional study of neutral and anionic AlO(n) and ScO(n) with high oxygen content.

The electronic and geometrical structures of neutral and negatively charged AlO(5), AlO(6), AlO(7), AlO(8), AlO(9), AlO(10), AlO(11), AlO(12), AlO(15), AlO(16), and AlO(18) along with the corresponding series of ScO(n) and ScO n- oxides were investigated using density functional theory with generalized gradient approximation. We found that these species possess geometrically stable isomers for all values of n = 5-12, 15, 16, 18 and are thermodynamically stable for n = 5-7. The species with n = 16 are found to be octa-dioxides M(η(1)-O(2))(8) while the species with n = 15 and 18 are penta-ozonides (η(2)-O(3))M(η(1)-O(3))(4) and hexa-ozonides M(η(1)-O(3))(6), respectively. Geometrical configurations of a number of the lowest total energy states of Al and Sc oxides are different. Especially, drastic differences are found for the anion AlO n- and ScO n- pairs at n = 9, 10, and 11. The Sc-O bonds are longer than the Al-O bonds by ≈0.2 Å, which, in turn, slightly affects the corresponding interoxygen bond lengths. The charges on metal atoms are close to +2e in both Al series and to +1.5e in both Sc series. As an extra electron is delocalized over ligands in the presence of a large positive charge on the metal atom of the anions, the electron affinity (EA) of the neutrals along with the ionization energies of the anions are large and exceed the EAs of the halogen atoms in a number of cases.

Dimerization of defect fullerenes and the orientational phase transition in oxidized C60 fullerite.

Oxidized fullerite was obtained by heating a fullerite sample intercalated with oxygen, (O2)0.44C60, up to 300 degrees C. Orientational phase transitions in the oxidized fullerite are studied using differential scanning calorimetry (DSC) and have been found to possess a specific enthalpy whose value is lower by 25% than in the initial (O2)0.44C60 sample. In order to find possible reasons for hindrance to the buckyball rotations, we performed optimizations of defect buckyball fullerenes C60-n with different distributions of vacancies along with the dimers C60-n-C60-n and C60-C60-n for n = 1-4 using density functional theory with generalized gradient approximation. We found that the dimerization energy ranges from 1.07 eV (C58-C58) to 6.56 eV (C56-C56) and from 1.81 eV (C60-C58) to 4.29 eV (C60-C56), respectively. The formation of such dimers, which could in addition interact with defect buckyball cages and form larger aggregates, is to be related to the lowering of the orientational transition enthalpy.

Structure and spectroscopic properties of iron oxides with the high content of oxygen: FeO(n) and FeO(n)(-) (n = 5-12).

The electronic and geometrical structures of oxygen-rich neutral and negatively charged FeO(5), FeO(6), FeO(7), FeO(8), FeO(9), FeO(10), FeO(11), and FeO(12) clusters were obtained using density functional theory with generalized gradient approximation. With the exception of FeO(11) and FeO(12), all clusters are found to possess a large number of isomers composed of oxo, peroxo, superoxo, and ozonide fragments that are closely spaced in total energy, especially for n = 7 and 8. The preferable structures of FeO(12) are composed of superoxo groups with different orientations. All the neutral species possess rather large electron affinities, which range from 3.24 eV (FeO(8)) to 3.95 eV (FeO(5)). Although all of the lowest energy states were found to possess positive vibrational frequencies and thus are geometrically stable, the states are thermodynamically unstable against dissociation to FeO(4) + (n - 4)/2 O(2) for n = 6, 8, 10, and 12 and FeO(5) + (n - 5)/2 O(2) for n = 7, 9, and 11. In particular, the decay of FeO(12) is exothermic by 34 kcal/mol.