First-principles Study Of The Correlation Between Host Components And Properties Of Cubic Perovskite Compounds

In this paper,we constructed 200 kinds of cubic perovskite halides and 30 kinds of cubic perovskite oxides and predicted the principle of the properties of these 230compounds depending on the atomic number.As implemented in CRYSTAL09 program based on first-principles calculation,the lattice constants,elastic constants,system energies,and bandgaps are researched,verifying the changing rules and supporting the theoretical basis for later experimental synthesis.The main research and conclusions of this paper are as follows:First part,by the basis of various elements and the determined optimization parameters,we calculated the lattice constants,bandgaps,system energies and elastic properties of 200 cubic perovskite compounds IAIIA?VIIA?₃?IA=Li,Na,K,Rb,Cs;IIA=Be,Mg,Ca,Sr,Ba;VIIA=F,Cl,Br,I?.First,the larger radius of the alkaline-earth metal ion in the center of the cubic lattice caused crystal lattice loses the equilibrium structure.In this situation,the site of A ion at the vertex of cubic lattice and the site of B ion at the center of the cubic lattice will be exchanged,this new equilibrium structure was named as“exchanged structure”.We choose the stable structure from“un-exchanged structure”and“exchanged structure”by using the principle that the more stable structure has lower energy.From the point of view mechanical property,the elastic modulus of the KBX₃,RbBX₃ and CsBX₃?B=Be,Mg,Ca,Sr,Ba;X=F,Cl,Br,I?compounds decreases with increasing radius of the central ion of the cubic crystal,showing that lattice of these compounds is“un-exchanged structure”.But we find unusual value increased data points in the trend that bulk elastic modulus of LiBX₃ and NaBX₃?B=Be,Mg,Ca,Sr,Ba,X=F,Cl,Br,I?compounds decreases with increasing radius of the central ion of the cubic crystal,because the site of A and B have been exchanged.The bandgaps of the ABF₃,ABCl₃,ABBr₃ and ABI₃ series compounds decrease with increasing atomic numbers of A and B ions.It is worthwhile to note that the bandgaps of partly compounds is decreasing when the atomic number is increasing.Second part,30 cubic-type perovskite oxides with the general formula IIAIVBO₃?IIA=Be,Mg,Ca,Sr,Ba;IVB=Ti,Zr,Hf?have been systematically studied using the first-principles methods.The relationship between the lattice constants,bandgaps,elastic properties and the varied atomic number of the metal cations are studied.The conclusion is consistent with the halide.