Basis set convergence of the Hartree-Fock and the correlation energy is
examined for the hydrogen bonded infinite bent chains (HF)_infinity and
(HCl)_infinity. We employ series of correlation consistent basis sets up to
quintuple zeta quality together with a coupled cluster method (CCSD) to
describe electron correlation on ab initio level. The Hartree-Fock energy
converges rapidly with increasing basis set quality whereas the correlation
energy is found to be slowly convergent for the same series of basis sets. We
study basis set extrapolation for (HF)_infinity and (HCl)_infinity and show
that it substantially enhances the accuracy of both the Hartree-Fock and the
correlation energy in extended systems.Comment: 12 pages, 4 figures, 4 tables, LaTeX, corrected typo