An ab initio study of structure and stability of Al₂F₂ molecule

Possible isomers of Al₂F₂ molecule are shown to exist by ab initio molecular orbital calculations at UMP2/6-311G(d) level. The values of energy at UMP2/6-311G(d) and UQCISD(T)/6-311 + G (3df)// UMP2/6-311G(d) level of the theory show that the isomer that has D_2h symmetry and¹A_g electronic state is the most stable equilibrium geometry. In the isomer, the Al-F bond length is 0.19074 nm, and the bond angles Al-F-Al and F-Al-F are 104.62° and 75.38°, respectively. Two strong vibrations have been found at 441.27 cm^-1 and 401.93 cm^-1. These results are in agreement with experimental ones. Analyses of electronic structure show that the active positions are on the Al atoms, and are main additive areas where it reacts with other compounds. The dimerization energies at UMP2/6 - 311G(d) and UQCISD(T)/6-311 + G(3df)//UMP2/6-311G(d) levels are -75.01 kJ/mol and -66.13 kJ/mol, respectively, and are in agreement with those in the literature. The results show that the dimerization of AlF is thermodynamically favored.