First Principle Study On The Structure And Property Of ?A And ?B Metal Phosphide

Metal phosphides are characterized by low cost,high activity,and excellent electronic properties,which plays an important role in new energy and electronic materials fields.In this work,we studied the structural,thermodynamic,electronic and mechanic properties of MP_x?M=Mg,Ca,Sr,Zn,Cd?which have been synthesized previously with the first-principle and accumulated the fundamental data,so as to discover their excellent applying to founctional materials.Employing VASP code based on DFT theory,we obtained a series of structural properties of compounds we calculated.As the metal fraction increases,the configuration of the P atom will change from a three-dimensional grid to a layered grid to a one-dimensional chain and then to an isolated P atom.Metal atoms coordinate with P atoms to form etrahedral,hexahedral and pentahedron structures.In the IIA?Mg,Ca,Sr?phosphides,a-SrP₃ and CaP₃ show semi-metal performance.Ia???-Mg₃P₂ andb-SrP₃ with the direct band gap value of 1.603 eV and 0.371 eV respectively,imply a potential application to photovoltaic and photoelectric materials.Pn???m-Mg₃P₂ and CaP have similar bandgap value?1.101 eV and 1.141 eV,respectively?to silicon,which have potential application in the novel chip and integrated circuit.In the IIB?Zn,Cd?phosphides,b-ZnP₂ anda-Zn₃P₂ with the direct gap value of 0.745 and 0.304 eV respectively,indicate a promising application to infrared absorption device.P4₂/nmc-Cd₃P₂and Ia???-Cd₃P₂ is semimetals,which offer a possibility to prepare the high-temperature superconductors.The strong P-P covalent bonds are formed between the P atoms in structures which metal proportion less than 0.6.However,the structures with metal content of 0.6 don't reveal covalent property between the P atoms.The interactions between the metal and the P atoms hold primarily ionic features and partially covalent characters.Moreover,in the same metal phosphide system,as the proportion of the metal increases,the covalent interaction between the P atoms gradually weakens,and the interaction between the metal and the P atoms gradually decreases.