University of Vienna, Faculty of Physics and Center for Computational Materials Science, Sensengasse 8/12, A-1090 Wien, Austria.
J Chem Phys. 2012 Feb 21;136(7):074701. doi: 10.1063/1.3684891.
The structural, energetic, and magnetic properties of Pt atoms and dimers adsorbed on a Ni-supported graphene layer have been investigated using density-functional calculations, including the influence of dispersion forces and of spin-orbit coupling. Dispersion forces are found to be essential to stabilize a chemisorbed graphene layer on the Ni(111) surface. The presence of the Ni-substrate leads not only to a stronger interaction of Pt atoms and dimers with graphene but also to a locally increased binding between graphene and the substrate and a complex reconstruction of the adlayer. The stronger binding of the dimer also stabilizes a flat adsorption geometry in contrast to the upright geometry on a free-standing graphene layer. These effects are further enhanced by dispersion corrections. Isolated Pt adatoms and flat dimers are found to be non-magnetic, while an upright Pt dimer has strongly anisotropic spin and orbital moments. For the clean C/Ni(111) system, we calculate an in-plane magnetic anisotropy, which is also conserved in the presence of isolated Pt adatoms. Surprisingly, upright Pt-dimers induce a re-orientation of the easy magnetic axis to a direction perpendicular to the surface, in analogy to Pt(2) on a free-standing graphene layer and to the axial anisotropy of a gas-phase Pt(2) dimer.
使用密度泛函计算研究了吸附在 Ni 支撑石墨烯层上的 Pt 原子和二聚体的结构、能量和磁性质，包括色散力和自旋轨道耦合的影响。发现色散力对于稳定 Ni(111)表面上化学吸附的石墨烯层是必不可少的。Ni 衬底的存在不仅导致 Pt 原子和二聚体与石墨烯的相互作用更强，而且导致石墨烯与衬底之间的局部结合增强和吸附层的复杂重构。二聚体更强的结合也稳定了平面吸附几何形状，与自由-standing 石墨烯层上的垂直几何形状形成对比。这些效应通过色散修正进一步增强。孤立的 Pt adatoms 和平面二聚体被发现是非磁性的，而垂直的 Pt 二聚体具有强烈各向异性的自旋和轨道矩。对于清洁的 C/Ni(111)系统，我们计算了面内磁各向异性，即使存在孤立的 Pt adatoms，该各向异性也得以保留。令人惊讶的是，垂直的 Pt 二聚体将易磁化轴的方向诱导到垂直于表面的方向，类似于自由-standing 石墨烯层上的 Pt(2)和气相 Pt(2)二聚体的轴向各向异性。
