陶瓷金属界面(无机材料结构和性能)的

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'陶瓷金属界面(无机材料结构和性能)的'
张 文 清 中国科学院上海硅酸盐研究所 e-mail: wqzhang@mail.sic.ac.cnShanghai Institute of Ceramics, CAS 课题的总体进展 项目时间: 2004.7 – 2005.9I. 陶瓷/金属界面 Ag/Al2O3, Au/Al2O3界面的计算已经完成. 文章Phys. Rev B接受; NiAl/Al2O3界面的计算进展正在进行, 但不太顺利.II. 热电材料掺杂极限及热电性能的研究 热电材料CoSb3中的单掺杂质的掺杂极限 - 已完成; 美国MRS年会邀请报告; Phys Rev Letters (修改中). CoSb3中的多掺杂问题 - 正在进行之中; 掺杂后材料(多掺杂系统)的热电性能研究 – 需要较大的计算量. Interfaces in real materials are secondnormally very complex. phaseØAdditives for ceramic sintering grain ØMany different grain boundaries boundaryⅠØMismatch and mis-orientationØSecond phase formationØImpurity segregationØTri-junction grain boundary ⅡØ…… Shanghai Institute of Ceramics, CAS Ab Initio Computations for Metal/Alumina Interfaces Metal(111)/Al2O3(0001)C.Scheu, G.Dehm,M.Ruhle, Phil. Mag. 78, 439 (1998). Ab Initio Computations for Metal/Alumina InterfacesComputational Method - First principles density functional theory ? Kohn-sham equation solved from first principles for metal/alumina interface. ? Self-consistent solutions for electron potential and electron density distribution. -- Essential for interface with mixed metallic-covalent-ionic interaction! ? First principles techniques: * Self-consistent local orbital (SCLO) Method * Full-potential linearized augmented plane wave method (FLAPW) * Pseudopotential methods – Vienna ab-initio simulation program (VASP) ? Primary approximation - electron exchange-correlation treated in the local density approximation (LDA) or the generalized gradient approximation (GGA). Al2O3 bulk O-termination Al-termination (Stoichiometric) Al2-termination Pseudopotential Computations for Metal/Alumina InterfacesTop view of the Al2O3(0001) surfaceInterfacial Structure: When lattice constants match O H Al v Metal atop oxygen sites as shown. v Slide metal to Al (H) sites for different initial configuration. fcc(111)(?3x ?3)/Al2O3(0001)(1x1) When lattice constants don’t match: Two of the ways of uniform strain to commersuration S tretch Metal Type I interface Stretch Compress Metal Al2O3Type II interface CommensurationExperimental Interfacial StabilitylAg/Al2O3 Interface: depend on oxygen partial pressurelAu/Al2O3 interface: don’t depend on oxygen partial pressure J. Feng, W. Zhang, W. Jiang, Phys. Rev. B (2005), in press. 中国科学院上海硅酸盐研究所 Interface with When lattice constants don’t match misfit dislocation Metal atoms atop Al Lattice Overlay (no relaxation) Metal atoms in hollows Oxygen AluminumMetal atoms Metalatop O ØThe metal and Al2O3 atoms will attempt to strain into commensuration to minimize energy . ØCommensuration results from misfit dislocations typically. ØWe must strain uniformly to commensuration – valid only for thin films ØMoral: Trust only results insensitive to surface strain. 工作进展需要计算的系统大小 Ni/(Al2O3)_O 678atoms/cell Ni/(Al2O3)_Al 705atoms/cell方法及进展 Siesta code is employed; Parallel computation must be done; (Siesta + MPI+ BLACS/ ScaLapack). ? parallel program works 1. Parallel efficiency needs to be improved; 2. Siesta code: slow self-consistency – code improvement. 计算工作仍在进行中! Heat source Active cooling P N P Ntne Heat sink Heat sinkrruC - + R Power generation Refr
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