Convergence of the electronic density for a target region in cluster models of a NH$$_3$$ molecular crystal

Abstract In this paper we illustrate the advantage of addressing size-intensive properties target regions without first converging ground-state energy that region. We use local occupied and virtual orbitals to separate orbital space NH $$_3$$ 3 clusters into an for region (a central molecule) remaining cluster. Convergence characteristics Hartree–Fock (HF) and, indirectly, electronic density are shown. The calculations although will not converge with cluster size, will. convergence is subsequently exploited obtain HF dipole moments CC2-in-HF vertical excitation energies. For these seen upon inclusion approximately three shells beyond This shows a can be investigated energy. further show minimal basis description outer sufficient capture correct interaction possibility computing using converged density, requiring in itself, currently underexploited feature.