Ab initio investigation of the ground and lowest excited states of the YAl molecule

Ab initio CASSCF and MRCI (single and double excitations plus Davidson correction) calculations have been performed for the yttrium aluminide molecule YAl. The potential energy curves of 10 molecular electronic states in the representation (2S+1)Lambda((+/-)) have been calculated along with the corresponding electronic energy with respect to the ground state T-e, the harmonic frequency omega e, the internuclear distance R-e, the rotational constant B-e, and the permanent dipole moment have been investigated for the considered electronic states. To the best of our knowledge, this study represents the first theoretical investigation of the electronic structure of the low lying excited states of YAl. The ground state equilibrium bond length, the vibrational frequency (with and without the anharmonic correction) and the dissociation energy have also been investigated by different density functional methods DFT using different basis sets. The vibrational levels of different states have been studied using canonical approach. Comparison of the present results with the single experimental study for the ground state X-3 Sigma(-) and the excited state (2)(3)Sigma(-) shows very good agreement.