#### Abstract

A self-energy-functional approach is applied to construct cluster approximations for correlated lattice models. It turns out that the cluster-perturbation theory [D. Sénéchal *et al.*, Phys. Rev. Lett. **84**, 522 (2000)] and the cellular dynamical mean-field theory [G. Kotliar *et al.*, Phys. Rev. Lett. **87**, 186401 (2001)] are limiting cases of a more general cluster method. The results for the one-dimensional Hubbard model are discussed with regard to boundary conditions, bath degrees of freedom, and cluster size.

- Received 10 March 2003

DOI:https://doi.org/10.1103/PhysRevLett.91.206402

©2003 American Physical Society