Ground state of Li and Be${}^{+}$ using explicitly correlated functions

Abstract

We compare the explicitly correlated Hylleraas and exponential basis sets in the evaluations of ground state of Li and Be${}^{+}$. Calculations with Hylleraas functions are numerically stable and can be performed with the large number of basis functions. Our results for ground state energies $-7.47806032391010(32)$, $-14.32476317679043(22)$ of Li and Be${}^{+}$ correspondingly, are the most accurate to date. When small basis set is considered, explicitly correlated exponential functions are much more effective. With only 128 functions we obtained about $10^{-9}$ relative accuracy, but the severe numerical instabilities make this basis costly in the evaluation.

15 pages

References in corpus (1)

• Two-center two-electron integrals with exponential functions