Combination of the single-double–coupled-cluster and the configuration-interaction methods: Application to barium, lutetium, and their ions

A version of the method of accurate calculations for few-valence-electron atoms which combines linearized single-double–coupled-cluster method with the configuration-interaction technique is presented. The use of the method is illustrated by calculations of the energy levels for Ba, ${\mathrm{Ba}}^{+}$, Lu, ${\mathrm{Lu}}^{+}$, and ${\mathrm{Lu}}^{2+}$. Good agreement with experiment is demonstrated and comparison with previous version of the method [M. S. Safronova et al., Phys. Rev. A 80, 012516 (2009)] is made.