The paper by S. Cahangirov et al. explores the stability and properties of two-dimensional (2D) honeycomb structures of silicon (Si) and germanium (Ge) using first-principles calculations. The authors demonstrate that both materials can form stable, low-buckled honeycomb structures, similar to graphene, which exhibit linear band crossings at the Fermi level, leading to Dirac-like behavior for charge carriers. These structures are ambipolar, meaning they can support both electron and hole carriers. The study also investigates the electronic and magnetic properties of armchair and zigzag nanoribbons of Si and Ge, which show size and orientation-dependent behavior. The results suggest that these materials could have significant applications in nanodevices due to their unique properties. The stability of the low-buckled honeycomb structures is confirmed through phonon dispersion curves and finite temperature molecular dynamics simulations. The paper highlights the potential for Si and Ge nanoribbons to exhibit both semiconducting and metallic properties, depending on their width and edge termination, making them promising candidates for various device applications.The paper by S. Cahangirov et al. explores the stability and properties of two-dimensional (2D) honeycomb structures of silicon (Si) and germanium (Ge) using first-principles calculations. The authors demonstrate that both materials can form stable, low-buckled honeycomb structures, similar to graphene, which exhibit linear band crossings at the Fermi level, leading to Dirac-like behavior for charge carriers. These structures are ambipolar, meaning they can support both electron and hole carriers. The study also investigates the electronic and magnetic properties of armchair and zigzag nanoribbons of Si and Ge, which show size and orientation-dependent behavior. The results suggest that these materials could have significant applications in nanodevices due to their unique properties. The stability of the low-buckled honeycomb structures is confirmed through phonon dispersion curves and finite temperature molecular dynamics simulations. The paper highlights the potential for Si and Ge nanoribbons to exhibit both semiconducting and metallic properties, depending on their width and edge termination, making them promising candidates for various device applications.