Chemisorption of organics on platinum. 1. The interstitial electron model
Chemisorption of organics on platinum. 1. The interstitial electron model
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DOI：
10.1021/jp9825260
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发表时间：
1998-11-19
影响因子：
3.3
通讯作者：
Goddard, WA
中科院分区：
文献类型：
--
作者：
Kua, J;Goddard, WA
利用量子力学第一原理（非局域密度泛函理论），研究了铂原子簇的成键和电子态。这些计算表明，在间隙电子模型（IEM）中，(i)来自四面体四个原子的6s价轨道结合在四面体中心形成一个间隙键轨道，该轨道被两个电子占据，形成间隙键（IEB）； （ii）来自每个原子的5d价轨道形成一个足够密集的成键和反键带，最佳占据是高自旋（Hund规则）或接近于高自旋。（iii）有机分子与Pt表面的键导致在单个Pt原子上形成与d轨道的共价键。这个简单的模型解释了所研究的几乎所有簇的成键和最低电子态。IEM表明，在三维面心立方（fcc）体系中，IEB中的每个原子都有两个电子，剩下的8个价电子在类d轨道上。对于体Pt，这导致6s(2)5d(8)有效电子构型。IEM表明Pt的（111）表面具有6s(1)5d(9)的有效电子构型。这表明，为了模拟Pt（111）表面的化学性质，我们应该使用导致（6s）(1)(5d)(9)结构的簇。这表明，一个具有8个原子的简单平面簇的间隙电子表面模型（IESM）可以用来模拟Pt（ll）表面的化学性质。这在随附的论文（第2部分）中用于检查Pt（111）上化学吸附的CHx和C2Hx物种。
Using first principles quantum mechanics (nonlocal density functional theory), we studied the bonding and electronic states for clusters of Pt atoms. These calculations suggest the interstitial electron model (IEM) in which (i) the 6s valence orbitals from the four atoms of a tetrahedron combine to form an interstitial bonding orbital at the center of the tetrahedron that is occupied by two electrons to form the interstitial electron bond (IEB), (ii) the 5d valence orbitals from each atom form a band of bonding and antibonding states sufficiently dense that the optimum occupation is high spin (Hund's rule) or nearly so, and (iii) bonds of organics to the Pt surface lead to covalent a bonds to d orbitals localized on individual Pt atoms. This simple model explains the bonding and lowest electronic state of essentially all clusters studied. The IEM suggests that the bonding in three-dimensional face-centered cubic (fcc) systems has two electrons from each atom in the IEB, leaving the remaining eight valence electrons in d-like orbitals. For bulk Pt, this leads to a 6s(2)5d(8) effective electronic configuration. The IEM suggests that the (111) surface of Pt would have a 6s(1)5d(9) effective electronic configuration. This suggests that to model the chemistry of the Pt(111) surface we should use clusters leading to the (6s)(1)(5d)(9) configuration. This suggests the interstitial electron surface model (IESM) in which a simple planar cluster with eight atoms serves to model the chemistry of the Pt(lll) surface. This is used in the accompanying paper (part 2) to examine CHx and C2Hx species chemisorbed on Pt(111).