Studies On Novel Nitride Functional Materials

Functional materials have been widely used in various fields of modern industry,and the design and synthesis of new multi-functional materials are one of the hot research topics in materials science.In this paper,particle swarm optimization?pso?based crystal structure prediction technique is used to search for novel nitride functional materials.By combining density functional theory with first-principles calculation method,the physical properties of the new material are calculated,and the mechanical properties,electronic properties and optical properties of the stable crystal material under different pressures are studied.It provides theoretical support for further research or experimental synthesis.The main research results of this paper are as follows:1.Five crystal structures of HeN₃ with high energy density were proposed,which were C2/m-I-HeN₃ at 300 GPa,P21/c-HeN₃ and R-3c-HeN₃ at 200 GPa,R-3m-HeN₃ at 100 GPa,and C2/m-II-HeN₃ at 40 GPa.In the structure of R-3m-HeN₃,there are'N6'rings that similar with benzene rings.In the'N6'ring,all the N atoms are connected with N-N.there is a very large energy difference between N-N?40 kcal/mol?and N?N?225 kcal/mol?,so,R-3m-HeN₃ break down to form the nitrogen N₂ will release a lot of energy,which suggests that R-3m-HeN₃ might be a potential of high energy density materials.2.A new transition metal nitride MoN₆ is also proposed.The MoN₆ structures Im-3m-MoN₆,R-3m-MoN₆ and Pm-3-MoN₆ have mechanical stability and dynamic stability under the pressure of 0 GPa,50 GPa and 100 GPa.MoN₆ will undergo a phase transition from R-3m-MoN₆ to Pm-3-MoN₆ when the pressure increase from 50 GPa to 100GPa.In the structure of R-3m-MoN₆,there are also'N6'rings similar to benzene rings,which are similar to R-3m-HeN₃,so MoN₆ may become a potential material with high energy density.The elastic properties calculation results of MoN₆ show that the deformation resistance and hardness of MoN₆ will increase with the increase of pressure.The calculation results of poisson ratio and energy band structure of MoN₆ show that MoN₆ is a metal material.3.The properties of K₄ phosphorus under pressure and strain were studied.It is determined that the mechanical stability and dynamic stability of K₄ phosphorus under isotropic pressure can reach 7 GPa.The ideal tensile strength of K₄ phosphorus is 8.5 GPa and the strain is 0.3.The mechanical properties of K₄ phosphorus were studied by calculating the elastic constants.The anisotropy of K₄ phosphorus increases with the increase of pressure.The density of K₄ phosphorus increases with increasing pressure.As the pressure increases from 0 GPa to 7 GPa,the average sound velocity decreases by 11.36%and the Debye temperature decreases by 7.34%,so it can be concluded that the covalent bond strength of K₄ phosphorus decreases with the increase of pressure.As can be seen from the band structure,K₄ phosphorus is an indirect semiconductor.By studying the effect of pressure and strain on K₄ phosphorus band gap,it can be concluded that no matter K₄ phosphorus is pressurized or strained,the band gap will become smaller.By studying the light absorption capacity of K₄ phosphorus,it can be concluded that all the strong absorption coefficients of K₄ phosphorus are in the visible range.Therefore,K₄ phosphorus has a good absorption ability to visible light.K₄ phosphorus expands the research scope of photoelectric materials in visible light region,providing a theoretical basis for finding new photoelectric materials.