Abstract
Potential energy curves for the lowest electronic states of LaB and LaB- have been calculated by ab initio calculations. The diffusion Monte Carlo method has been employed in combination with three different trial functions. Spectroscopic constants have also been numerically derived for the neutral molecule and compared with the only available theoretical work;([)(19]) however, predictions are provided for the corresponding constants for the anionic species which have not been reported yet. Our calculations suggest the high spin quintet state of LaB as the ground state with the triplet state higher in energy irrespective of the type of the functional used. This suggestion is in good accordance with the previous theoretical results calculated at B3LYP/LANL2DZ level of theory, whereas it contradicts with the prediction based upon B3LYP/SDD calculations in the same study. Moreover, variations of the permanent dipole moments as a function of the internuclear separations for the two electronic states of the neutral molecule have been studied and analyzed.