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温俊青  夏涛  王俊斐 《物理学报》2014,63(2):23103-023103
采用密度泛函理论方法,在BPW91/LANL2DZ水平下详细研究了Pt n Al(n=1—8)团簇的几何结构、稳定性和电子性质.同时,分析了团簇的结构演化规律、平均结合能、二阶能量差分、能隙、磁性、Mulliken电荷和电极化率.结果表明:除Pt2Al外,所有Pt n Al(n=1—8)团簇的基态几何结构都可以用Al原子替换Pt n+1基态构型中的Pt原子得到,且Al原子位于较高的配位点上.二阶能量差分、能隙的分析结果表明,PtAl和Pt4Al团簇相对其他团簇具有较高的稳定性.Mulliken电荷分析表明,Al原子所带的电荷转移到Pt原子上,Al原子是电荷的捐赠者.磁性的分析说明,单个Al原子的加入对Pt n团簇的平均每原子磁矩随尺寸的变化趋势没有影响,但总体上降低了Pt n团簇的平均磁矩.极化率的研究表明,富Pt团簇的非线形光学效应强,容易被外场极化.  相似文献   
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The structural, elastic, phonon and electronic properties of a MnPd alloy have been investigated using the first-principles calculation. The calculated lattice constants and electronic structure agree well with the experimental results. The microscopic mechanism of the diffusionless martensitic transition from the paramagnetic B2 (PM-B2) phase to the antiferromagnetic L10 (AFM-L10) phase through the intermediate paramagnetic L10 (PM-L10 ) phase has been explored theoretically. The obtained negative shear modulus C′= (C11-C12)/2 of the PM-B2 phase is closely related to the instability of the cubic B2 phase with respect to the tetragonal distortions. The calculated phonon dispersions for the PM-L10 and AFM-L10 phases indicate that they are dynamically stable. However, the AFM-L10 phase is energetically most favorable according to the calculated total energy order, so the PM-L10 →AFM-L10 transition is caused by the magnetism rather than the electron-phonon interaction. Additionally, the AFM-L10 state is stabilized through the formation of a pseudo gap located at the Fermi level. The calculated results show that the CuAu-I type structure in the collinear antiferromagnetic state is dynamically and mechanically stable, thus is the low temperature phase.  相似文献   
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采用密度泛函理论(DFT)方法,在BPW91/LANL2DZ水平下详细研究了PdnAl±(n=1—8)团簇的几何结构、稳定性和电极化率,并与Pdn+1和PdnAl(n=1—8)团簇进行了比较.结果表明:除n=6,8外,PdnAl团簇和Pdn+1团簇的基态结构保持了相同的构型,除Pd2Al±和Pd6Al+外,PdnAl±团簇的基态结构与PdnAl团簇的保持了相同的结构.且在PdnAl和PdnAl±团簇基态结构中,Al原子位于较高的配位点上.分裂能和二阶能量差分的分析结果表明Pd4,Pd3Al和Pd3Al±团簇相对其他团簇具有较高的稳定性.极化率的研究表明富Pd团簇的非线性光学效应强,容易被外场极化.Pd6,Pd5Al和Pd3Al±团簇的极化率各向异性不变量为最小值,说明相应团簇对外场的各向异性响应最弱,各方向的极化率大小变化不大.  相似文献   
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