哈密顿动力学的优越性

偶然拜读了贵刊在2006年第5期中刊登的文章《哈密顿和哈密顿力学》后颇有感触,该文谈及了哈密顿动力学的优越性问题,为了能够让读者更为全面清楚地了解这一问题,本文将哈密顿动力学与拉格朗日动力学进行比较再进一步做一些补充和总结。     

Full-Heusler合金X2YGa(X=Co,Fe,Ni;Y=V,Cr,Mn)的电子结构、磁性及半金属特性的第一性原理研究

利用基于密度泛函理论的全势线性缀加平面波方法,结合广义梯度近似,对full-Heusler X₂YGa(X=Co,Fe,Ni;Y=V,Cr,Mn)合金的电子结构、磁性及半金属特性进行了研究,并讨论了自旋-轨道耦合作用对它们的影响.计算结果表明,自旋-轨道耦合作用对full-Heusler X₂YGa(X=Co,Fe,Ni;Y=V,Cr,Mn)合金的电子结构,磁性与半金属特性的影响很小. 当未考虑自旋-轨道耦合作用时,Co₂VGa,Co₂CrGa,和Fe₂CrGa合金为半金属或准半金属铁磁体,加入自旋-轨道耦合作用后体系的自旋极化率将降低1%左右, 它们依然保持很高的自旋极化率.Fe₂MnGa,Co₂MnGa,Ni₂CrGa和Ni₂MnGa合金为一般铁磁体,Fe₂VGa和Ni₂VGa合金为顺磁体. 关键词： 半金属特性 自旋-轨道耦合 Heusler合金 全势线性缀加平面波方法(FLAPW)     

Electronic structures and magnetism of Fe nanowires on Cu（001） and Ag（O01）： A first-principles study

The electronic structures and magnetism of Fe nanowires along the [110] direction on Cu（001） and Ag（001） [Fe（nw）/Cu（001） and Fe（nw）/Ag（001）] are investigated by using the all-electron full-potential linearized augmented plane wave method in the generalized gradient approximation. It is found that the magnetic moment of Fe atom for the Fe（nw）/Cu（001） is 2.99#B, which is slightly smaller than that （3.02μB） for the Fe（nw）/Ag（001） but much larger than that （2.22μB） for the bcc iron. The great enhancement of magnetic moment in the Fe nanowires can be explained by the Fe d-band narrowing and enhancement of the spin-splitting due to a reduction in coordination number, From the calculated spin-polarized layer-projected density of states, it is found that the Fe 3d-states are strongly hybridized with the adjacent Cu 3d-states in the Fe（nw）/Cu（001）, and there exists a strong hybridization between the Fe sp-and the adjacent Ag 4d-states in the Fe（nw）/Ag（001）.