Ground-state molecular and electronic structures of group-IV nanoribbons, nanorings and nanotubes

Based on ab initio molecular orbital (MO) theory and first-principles band calculations, we systematically study the ground-state molecular and electronic structures of group-IV nanoribbons (NRBs), nanorings (NRGs) and nanotubes (NTBs) by substituting the honeycomb skeletal atoms with C, Si or Ge atoms. We then explore the energetics in the ground-state singlet–triplet (ST) crossover, particularly focusing on the configuration hybridization by electron correlation.