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 alpha~2 relativistic corrections(alpha= 1/c).With those corrections and the alpha~3 and alpha~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.
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