Ba置换对钙钛矿型氧化物CaMnO_3稳定性及电子结构的影响
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摘要
采用赝势法近似密度泛函理论的方法研究了重元素Ba置换钙钛矿型氧化物CaMnO_3的稳定性及电子结构.结果表明,Ba置换引入晶格畸变,且具有各向异性.Ba置换钙钛矿型氧化物CaMnO_3呈现明显的半导体特性,且其稳定性降低.Ba置换Ca位之后,钙钛矿型氧化物CaMnO_3仍然呈间接带隙型能带结构,自旋向上和自旋向下的电子能带带隙宽度分别减小到0.659 eV和0.655 eV,且经过Ba置换之后向导体转变.Ba置换CaMnO_3晶体中的电子主要在-37.5 eV,-18 eV,-16 eV,-5 eV～0 eV,1 eV附近形成能带,能级数量在-18 eV,-16 eV,-0.7 eV三个极值点依次降低.Ba置换钙钛矿型氧化物CaMnO_3价带中和导带中的电子能级弥散性不同,表明它们具有不同的有效质量.Mn p,O p和Mn d电子对钙钛矿型氧化物CaMnO_3费米面态密度具有较大的贡献,它们决定CaMnO_3材料的导电过程.
The stability and electronic structure of the heavy element Ba substituted perovskite type oxide CaMnO_3 have been studied by the psudo-potential approximation density funtional theory calculation method.The results show that the lattice distortion has been induced by Ba substitution and the distortion is anisotropic.The Ba substituted perovskite type oxide CaMnO_3 exhitbites semiconductor character and the stability decreases.The indirect band gap has been remained by Ba substitution for Ca site for the perovskite type oxide CaMnO_3 yet,the band gaps of the spin up electrons and the spin down electrons have been slightly decreased to 0.659 eV and 0.655 eV,respectively.The semiconductor to conductor transition has also been found.The electrons of the Ba substituted perovskite type oxide CaMnO_3 form energy bands near-37.5 eV,-18 eV,-16 eV,-5 eV～0 eV and 1 eV,and the peak values of the density of states curve decreases along with the energy regions of -18 eV,-16 eV and-0.7 eV.The dispersion characters of the bands within the valance bands and the conduction bands are much different,which indicate their diverse effective mass.The Mn p,O p and the Mn d electrons have contributtion to the density of states at the Fermi level,these electrons determine the conduction process of the titled oxide materials.
The stability and electronic structure of the heavy element Ba substituted perovskite type oxide CaMnO_3 have been studied by the psudo-potential approximation density funtional theory calculation method.The results show that the lattice distortion has been induced by Ba substitution and the distortion is anisotropic.The Ba substituted perovskite type oxide CaMnO_3 exhitbites semiconductor character and the stability decreases.The indirect band gap has been remained by Ba substitution for Ca site for the perovskite type oxide CaMnO_3 yet,the band gaps of the spin up electrons and the spin down electrons have been slightly decreased to 0.659 eV and 0.655 eV,respectively.The semiconductor to conductor transition has also been found.The electrons of the Ba substituted perovskite type oxide CaMnO_3 form energy bands near-37.5 eV,-18 eV,-16 eV,-5 eV～0 eV and 1 eV,and the peak values of the density of states curve decreases along with the energy regions of -18 eV,-16 eV and-0.7 eV.The dispersion characters of the bands within the valance bands and the conduction bands are much different,which indicate their diverse effective mass.The Mn p,O p and the Mn d electrons have contributtion to the density of states at the Fermi level,these electrons determine the conduction process of the titled oxide materials.
引文
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[5]Saiga Y,Suekuni K,Du B,et al.Thermoelectric properties and structural instability of type-I clathrate Ba8Ga16Sn30at high temperatures[J].Solid State Commun.,2012,152:1902.
[6]Zhao L D,Zhang B P,Li J F,et al.Enhanced thermoelectric and mechanical properties in textured ntype Bi2Te3prepared by spark plasma sintering[J].Solid State Sci.,2008,10:651.
[7]Shi X,Hong H,Li C P,et al.Low thermal conductivity and high thermoelectric figure of merit in n-type BaxYbyCo4Sb12double-filled skutterudites[J].Appl.Phys.Lett.,2008,92:182101.
[8]Fergus J F.Oxide materials for high temperature thermoelectric energy conversion[J].J.Euro.Ceram.Soc.,2012,32:525.
[9]Zhang R Z,Hu X Y,Guo P,et al.Thermoelectric transport coefficients of n-doped Ca Ti O3,Sr Ti O3and Ba Ti O3:A theoretical study[J].Physica B,2012,407:1114.
[10]Wang Y,Sui Y,Wang X J,et al.Seebeck coefficient of LnxCa1-xMnO3perovskites in paramagnetic state[J].Appl.Phys.A,2011,104:135.
[11]Wang Y,Sui Y,Su W H.High temperature thermoelectric characteristics of Ca0.9R0.1MnO3(R=La,Pr,…,Yb)[J].J.Appl.Phys.,2008,104:093703.
[12]Zhang F P,Lu Q M,Zhang X,et al.First principle investigation of electronic structure of Ca MnO3thermoelectric compound oxides[J].J.Alloy.Compd.,2011,509:542.
[13]Zhang F P,Zhang X,Lu Q M,et al.Electronic structure and thermal properties of doped Ca MnO3system[J].J.Alloy.Compd.,2011,509:4171.
[14]Zhang F P,Lu Q M,Zhang X,et al.Electrical transport properties of Ca MnO3thermoelectric compound:a theoretical study[J].J.Phys.Chem.Solids,2013,74:1859.
[15]Sanmathi C S,Takahashi Y,Sawaki D,et al.Microstructure control on thermoelectric properties of Ca0.96Sm0.04MnO3synthesized by co-precipitation technique[J].Mater.Res.Bull.,2010,45:558.
[16]Jiang Z N,Zhang F P,Zhang X,et al.Preparation and thermoelectric properties of the rare earths doped Ca0.95RE0.05MnO3(RE=Pr,Eu and Tb)oxide materials[J].Indian J.Pure&Appl.Phys.,2015,53:530.
[17]Zhang F P,Lu Q M,Zhang X,et al.Preparation and improved electrical performance of the Pr-doped Ca MnO3+δthermoelectric compound[J].Phys.Scr.,2013,88:035705.
[18]Sangjie Z B,Ye T,Ding N,et al.Theoretical study on the structures,stabilities and electronic properties of In Sin(n=2-15)clusters[J].J.At.Mol.Phys.,2017,34:649(in Chinese)[桑杰扎布,叶铁,卜肖宁,等.In Sin(n=2-15)团簇结构、稳定性与电子性质的理论研究[J].原子与分子物理学报,2017,34:649]
[19]Hou R,Li S T,Niu F,et al.Geometries,stabilities and electronic properties of the Ru Sin(n=1-6)cluster:A density functional investigation[J].J.At.Mol.Phys.,2016,33:252(in Chinese)[侯茹,李书婷,牛峰,等.Ru Sin(n=1~6)团簇的结构、稳定性和电子性质的密度泛函研究[J].原子与分子物理学报,2016,33:252]