  We propose two schemes for interpolation of the one-particle Green's function
(GF) calculated within coupled-cluster singles and doubles (CCSD) method for a
periodic system. They use Wannier orbitals for circumventing huge cost for a
large number of sampled k points. One of the schemes is the direct
interpolation, which obtains the GF straightforwardly by using Fourier
transformation. The other is the self-energy-mediated interpolation, which
obtains the GF via the Dyson equation. We apply the schemes to a LiH chain and
trans-polyacetylene and examine their validity in detail. It is demonstrated
that the direct-interpolated GFs suffer from numerical artifacts stemming from
slow convergence of CCSD GFs in real space, while the self-energy-mediated
interpolation provides more physically appropriate GFs due to the localized
nature of CCSD self-energies. Our schemes are also applicable to other
explicitly correlated methods capable of providing GFs.
