  We study the quasiparticle band structure of isolated, infinite HF and HCl
bent (zigzag) chains and examine the effect of the crystal field on the energy
levels of the constituent monomers. The chains are one of the simplest but
realistic models of the corresponding three-dimensional crystalline solids. To
describe the isolated monomers and the chains, we set out from the Hartree-Fock
approximation, harnessing the advanced Green's function methods "local
molecular orbital algebraic diagrammatic construction" (ADC) scheme and "local
crystal orbital ADC" (CO-ADC) in a strict second order approximation, ADC(2,2)
and CO-ADC(2,2), respectively, to account for electron correlations. The
configuration space of the periodic correlation calculations is found to
converge rapidly only requiring nearest-neighbor contributions to be regarded.
Although electron correlations cause a pronounced shift of the quasiparticle
band structure of the chains with respect to the Hartree-Fock result, the
bandwidth essentially remains unaltered in contrast to, e.g., covalently bound
compounds.
