A new approach for the determination of correlation energies in periodic extended systems is proposed using the high transferability of amplitudes and integrals from natural bond orbital coupled cluster (NBO CC) calculations performed for small subunits. It is shown that the NBO CC calculations can in fact deliver detailed correlated wave function information for extended periodic systems. As an example we apply the ideas presented in this paper to determine an estimate for the valence correlation energy in diamond at the CCSD level. (C) 2003 American Institute of Physics.