Abstract:
Explicitly correlated Gaussian functions have been used to perform very accurate variational
calculations for the ground states of 7Li and 7Li−. The nuclear motion has been explicitly included
in the calculations i.e., they have been done without assuming the Born-Oppenheimer BO
approximation . An approach based on the analytical energy gradient calculated with respect to the
Gaussian exponential parameters was employed. This led to a noticeable improvement of the
previously determined variational upper bound to the nonrelativistic energy of Li−. The Li energy
obtained in the calculations matches those of the most accurate results obtained with Hylleraas
functions. The finite-mass non-BO wave functions were used to calculate the 2 relativistic
corrections =1/c . With those corrections and the 3 and 4 corrections taken from Pachucki and
Komasa J. Chem. Phys. 125, 204304 2006 , the electron affinity EA of 7Li was determined. It
agrees very well with the most recent experimental EA