First-principles Study On The Structural And Electronic Properties Of Boron Bioxide

Pressure has an important effect on the structures and properties of the material.It is an important mean of exploring new functional materials,such as superhard,superconducting,thermoelectric and other materials.The material will undergo phase transition because of the change in the atomic interaction of the structures under high pressure,thus exhibiting novel physical and chemical properties.Therefore,the study of the phase transition of pressure-induced structure not only could deeply understand the nature of the existing structure,but also get new physical phenomena and laws.In recent years,as continuously updating and developing,the theory of the theoretical method has become an effective way to find a new structure.In this paper,we use CALYPSO structure research and design method developed by our research group combined with the first-principles based on density functional theory.This method is based on the particle swarm optimization algorithm.The structure of the material information can be obtained only through providing the chemical ratio of the studied material and certain external conditions.At present,the CALYPSO structure prediction method realizes the structural design of three-dimensional crystal structure material,two-dimensional layered material,two-dimensional surface reconstruction and zero-dimensional cluster structure,which greatly enriches the structure phenomenon.Boron based on the B12 positive icosahedron as the basic structural unit is the only nonmetallic element in the third main group of the periodic table,which is used to make up the electron deficiency by means of unconventional,three central chemical bonds.The introduction of higher electronegativity elements?such as oxygen?will make boron more electron deficiencies under pressure,and thus effectively control its crystal structure and chemical bonds.The research will help to understand the formation of multi-center chemical bonds and the phenomenon of evolution.In this paper,The CALYPSO structure design method based on a global minimization of free energy surfaces were employed to perform structural searching for B₂ O compounds under high pressure and the following innovative results were obtained:1.Two thermodynamically stable phases of Cmmm and P-3 with space group were determined by the system of high-pressure structure.For compressed B₂ O,a Cmmm phase transforms into P-3 phase about 1.9 GPa.It is the first time that B12 icosahedral units occur to B₂ O,then B₂ O forms a layered structure P-3 containing a variety of chemical bonds under pressure with the icosahedra collapsing.2.The electronic calculation shows that both B₂ O structures exhibit metallic properties with covalent bonds.The electron-phonon interaction calculations predict that they all have superconducting properties with a superconducting transition temperature of 6.4 K and 6.2 K,respectively.