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Among the diversity of new materials, two-dimensional crystal structures have been attracting significant attention from the broad scientific community due to their promising applications in nanoscience. In this study we predict a novel two-dimensional ferromagnetic boron material, which has been exhaustively studied with DFT methods. The relaxed structure of the 2D-B 6 monolayer consists of slightly flattened octahedral units connected with 2c-2e B–B σ-bonds. The calculated phonon spectrum and ab initio molecular dynamics simulations reveal the thermal and dynamical stability of the designed material. The calculation of the mechanical properties indicate a relatively high Young's modulus of 149 N m −1 . Moreover, the electronic structure indicates the metallic nature of the 2D-B 6 sheets, whereas the magnetic moment per unit cell is found to be 1.59 μ B . The magnetism in the 2D-B 6 monolayer can be described by the presence of two unpaired delocalized bonding elements inside every distorted octahedron. Interestingly, the nature of the magnetism does not lie in the presence of half-occupied atomic orbitals, as was shown for previously studied magnetic materials based on boron. We hope that our predictions will provide promising new ideas for the further fabrication of boron-based two-dimensional magnetic materials. 

Abstract The structure and properties of two‐dimensional phosphoborane sheets were computationally investigated using Density Functional Theory calculations. The calculated phonon spectrum and band structure point to dynamic stability and allowed characterization of the predicted two‐dimensional material as a direct‐gap semiconductor with a band gap of ~1.5 eV. The calculation of the optical properties showed that the two‐dimensional material has a relatively small absorptivity coefficient. The parameters of the mechanical properties characterize the two‐dimensional phosphoborane as a relatively soft material, similar to the monolayer of MoS₂. Assessment of thermal stability by the method of molecular dynamics indicates sufficient stability of the predicted material, which makes it possible to observe it experimentally. 

A new metastable crystalline form of gallium has been computationally designed using density functional calculations with imposing periodic boundary conditions. The geometric and electronic structures of the predicted new allotrope were calculated on the basis of a diamond lattice in which all carbon atoms are replaced by gallium Ga₄tetrahedra. This form does not have any imaginary phonons, thus it is a metastable crystalline form of gallium. The new form of gallium is a metal and shows high plasticity and low‐melting temperature. Molecular dynamics simulations show that this form of gallium will melt at about 273 K with a sharp increase in temperature in the system during the melting process from 273 to 1800 K. This melting process is very different from conventional melting, where temperature stays the same until complete melting. That unusual melting can be explained by the fact that supertetrahedral gallium is a metastable structure that has an excess of strain energy released during melting. If made this new material may find many useful applications as a new low density metal with stored internal energy. © 2019 Wiley Periodicals, Inc.