The electronic and geometrical structure of aluminum fluoride anions AlF[sup [minus]][sub [ital n]], [ital n]=1--4, and electron affinity of their neutral parents
- Department of Chemistry, the University of Arizona, Tucson, Arizona, 85721 (United States)
The electronic and geometrical structure of AlF[sup [minus]], AlF[sup [minus]][sub 2], AlF[sup [minus]][sub 3], and AlF[sup [minus]][sub 4] as well as their neutral parents are determined at the unrestricted Hartree--Fock (UHF) and second-order unrestricted Moller--Plesset (UMP2) levels of theory. The results of the calculations are used for estimating the adiabatic electron affinity (E.A.) of the neutrals and fragmentation energies of both the neutrals and anions. All these characteristics were also recomputed using the UMP2/6-31+G* geometry at the fourth-order UMP4 level of theory. According to the results of the single-, double, triple-, and quadruple-excitation fourth-order Moller--Plesset (MP4SDTQ) calculations, the AlF molecule in the ground state has no positive E.A., AlF[sub 2] possesses a rather high E.A. value of 1.90 eV, and AlF[sub 3] has a smaller E.A. of 0.93 eV, whereas the last member in the series AlF[sub 4] possesses an extremely high E.A. of 7.96 eV. Such a large value is related to high stability of the anion towards fragmentation opposite to the neutral AlF[sub 4] whose dissociation energy is computed to be only 4--5 kcal/mol. It has been predicted that all the anions are rather stable towards detachment of a fluorine anion, and AlF[sup [minus]][sub 4] is the most stable in the series. The AlF molecule is able to attach an additional electron at large interatomic distances and form a stable anion. This indicates an increasing tendency to form resonances when the molecule is excited into a higher vibrational state. Our calculations also show that AlF in the lowest triplet state may attach an additional electron to form a metastable anion in the quartet state. This anion is predicted to be stable towards both detachment of the extra electron and dissociation. A similar increasing tendency to formation of resonance states with an additional electron with vibrational excitation is also predicted for AlF[sub 2].
- DOE Contract Number:
- FG03-93ER61605
- OSTI ID:
- 7307584
- Journal Information:
- Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 100:12; ISSN JCPSA6; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
74 ATOMIC AND MOLECULAR PHYSICS
ADIABATIC APPROXIMATION
AFFINITY
ALUMINIUM COMPOUNDS
ALUMINIUM FLUORIDES
ANIONS
CHARGED PARTICLES
DISTANCE
ELECTRONIC STRUCTURE
ENERGY LEVELS
EXCITED STATES
FLUORIDES
FLUORINE COMPOUNDS
GEOMETRY
HALIDES
HALOGEN COMPOUNDS
INTERATOMIC DISTANCES
IONS
MATHEMATICS
METASTABLE STATES
MULTIPLETS
RESONANCE
TRIPLETS