From Two‐ to Three‐Dimensional Structures of a Supertetrahedral Boran Using Density Functional Calculations

Abstract

With help of the DFT calculations and imposing of periodic boundary conditions the geometrical and electronic structures were investigated of two‐ and three‐dimensional boron systems designed on the basis of graphane and diamond lattices in which carbons were replaced with boron tetrahedrons. The consequent studies of two‐ and three‐layer systems resulted in the construction of a three‐dimensional supertetrahedral borane crystal structure. The two‐dimensional supertetrahedral borane structures with less than seven layers are dynamically unstable. At the same time the three‐dimensional superborane systems were found to be dynamically stable. Lack of the forbidden electronic zone for the studied boron systems testifies that these structures can behave as good conductors. The low density of the supertetrahedral borane crystal structures (0.9 g cm−3) is close to that of water, which offers the perspective for their application as aerospace and cosmic materials.

Molecular dynamics study of a new metastable allotropic crystalline form of gallium—supertetrahedral gallium

“…The calculated density of the supertetrahedral gallium is equal to 1.74 g/cm 3 , which is considerably lower than that of the usual structure of gallium 5.9 g/cm 3 , but it is higher the density of supertetrahedral aluminum (0.61 g/cm −1 ), supertetrahedral boron (0.92 g/cm −3 ), and T carbon (1.50 g/cm −1 ) . The calculated phonon spectrum is shown in Figure .…”

“…The rapid progress of science and technology constantly requires development of new materials with specific properties. In this respect, computational design provides relatively quick and low‐cost assessment of the structure and properties of new materials plays an indispensable role . Metastable materials are a new area of research that offers almost an infinite number of new materials with unusual and unexpected properties …”

“…According to quantum chemical calculations, the T d structure 1 (X = B) B 4 H 4 is kinetically stable despite the electron deficit in the system excluding formation of two‐center two‐electron (2c2e) bonds between all atoms . Therefore, boron tetrahedron is also could be used as a structural unit for the design of tetrahedral crystalline structures . Both aluminum and gallium tetrahedrons: Al 4 H 4 and Ga 4 H 4 correspond to a global minimum on the potential energy surface (PES).…”

“…Most importantly, new supertetrahedral materials are extremely light and that opens new potential application for these substances. Indeed, calculations of supertetrahedral structures of solid boron and aluminum showed that they possess dynamic stability and have amazingly low density with some of them being below the water density, as well as sufficiently high plasticity and elastic properties.…”

Electron‐Deficient Triborane and Tetraborane Ring Compounds: Synthesis, Structure, and Bonding

“…The tolerance of these rings for various electron numbers should result in interesting electronic properties.B alakrishnarajan and Hoffmann discussed the bonding in rhomboid B 4 compounds with various skeletal electron numbers, [7] and also analyzed the occurrence of the rhomboid B 4 motif in solid Na 3 B 20 and of analogous rhomboid Si 4 motifs in b-SiB 3 ,w here the connection of these electron-deficient units through (2c,2e) bonds leads to semiconducting chains.M ore recently,t wo-and three-dimensional structures formed by connecting tetrahedral B 4 units together were studied theoretically,a nd predicted to be good conductors. [112] Molecular B 3 and B 4 rings are also potential precursors to "borophen" (2D boron). [113,114] Hence,t here are strong indications that the integration of electron-deficient B 3 and B 4 rings in higher molecular architectures and materials will lead to interesting properties.B uilding upon the substantial research on individual electron-deficient B 3 and B 4 ring compounds,arational approach to such functional systems can now be envisioned.…”