First-principles Study Of The Strain-induced Semiconductor-metal Transitions In Skutterudite IrAs₃

Applying strain to materials can cause structural changes,which is a powerful method for designing novel materials in materials science research.The electronic state near the Fermi energy level of the material is closely related to the electronic orbital interaction of adjacent atoms in the crystal structure.The electron orbits reorganize under the action of the strain field,which causes the electronic properties of the material to change.Previous studies have shown that strain engineering is an effective and green method to regulate the properties of materials and has a great application prospect.With the rapid development of computer technology and the improvement of theoretical methods,the first-principles calculation methods based on density functional theory can simulate the changes of materials in the process of applying strain,and then explore the changes of the physical and chemical properties of materials under the applied strain field,providing powerful data support for the design of new materialsAs a kind of binary phosphorous compound with the chemical formula AB3(A=Ir,Co,Rh,etc.,B=As,P,Sb,etc.),skutterudite is the promising thermoelectric materials with excellent thermoelectric properties and is environmentally friendly.Previous studies have shown that metal doping is a good way to regulate the properties of skutterudite.Very recently,the Ba doping makes iridium pnictides IrAs3 and IrP3(BaxIr4X12)undergo a nonmetal-to-metal transition.However,the precise control of the position and the number of doped atoms are very challenging,and it is very easy to introduce impurities,and there are many obstacles in the experimental process.In view of the previous investigation of strain engineering,we speculate thatapplying strain may be another methods to achieve the metallization of these materials.In this paper,we mainly adopted the first-principles calculation method,selected skutterudite material IrAs3 as a representative,explored the strain-induced structural transformation,as well as the changes in crystal structure,electronic structure,and bonding mode during the transformation process.The following research results are obtained:1.The band gap of IrAs3 decreases gradually under the strain until it is completely closed.When the tensile strain is applied along the<100>direction,the change of band gap is the most sensitive.About 9%of uniaxial tensile strain can achieve the semiconductor-metal transition of IrAs3.Under the action of reverse compressive strain,the band gap is completely restored,indicating that the semiconductor-metal transition is reversible.2.The strain-induced octahedral Jahn-Teller effect and the fracture of the As4-rings are the fundamental causes of semiconductor-metal transition.In addition,the iridium atom with strong electronegativity in IrAs3 becomes electron acceptor under the effect of the octahedral field and strain field,and receives valence electrons from the As4-rings.3.Hydrostatic pressure can also induce the closure of band gap in IrAs3.However,strain engineering has more advantages over hydrostatic pressure in the semiconductor-metal transition of IrAs3.These research results will not only help understand the regulating effect of the strain on the structure and properties of skutterudite materials,but also establish an effective and economical method of strain-induced metallization,providing a new perspective for using strain engineering to design skutterudite materials with excellent performance.