Abstract:
Very accurate finite-nuclear-mass variational nonrelativistic calculations are performed for the lowest five
1D states (1s2 2p2, 1s2 2s1 3d1, 1s2 2s1 4d1, 1s2 2s1 5d1, and 1s2 2s1 6d1) of the beryllium atom (9Be). The
wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian functions. The
exponential parameters of the Gaussians are optimized using the variational method with the aid of the analytical
energy gradient determined with respect to those parameters. The calculations exemplify the level of accuracy
that is now possible with Gaussians in describing bound states of a four-electron system where some of the
electrons are excited into higher angular states