Nanostructures of Molybdenum, Chromium, and Tungsten Constructed by a Basic Structural Unit

We predicted a stable, zigzag chain structure of Molybdenum Mo, which, being a basic structural unit, can construct stable 0D or quantum dot (segments of atomic chains and rings), 1D (various infinite chains), quasi-1D (nanoribbons and nanotubes), and 2D (bilayers) structures entailing critical magnetic, elastic, and electronic properties. This zigzag chain, constituted by strong Mo-Mo covalent bonds, is a nonmagnetic semiconductor but undergoes an insulator-metal transition under compression acquiring a ferromagnetic state. Although Mo cannot form stable, suspended, 2D monolayers of a single atomic plane, parallel zigzag chains bound by metallic interchain interaction can construct stable bilayers of different symmetry, and also their stacks forming slabs. These bilayers, being elemental Dirac materials and displaying directional properties, clarify the ambiguous situation in recent studies synthesizing and/or predicting different 2D molybdenene structures. Notably, other Group VIB elements, chromium, and tungsten, also construct similar atomic chains and 2D bilayers with diverse physical properties. Intriguingly, an atomic chain structure serves as a building block for many low-dimensional materials with diverse physical properties, making it unique in nanoscience.