Iron clusters: Electronic structure and magnetism
Iron clusters: Electronic structure and magnetism
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铁团簇：电子结构和磁性
DOI：
10.1103/physrevb.24.5673
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发表时间：
1981
影响因子：
3.7
通讯作者：
R. P. Messmer
中科院分区：
文献类型：
--
作者：
Chiang Y. Yang;K. H. Johnson;D. Salahub;J. Kašpar;R. P. Messmer
用自洽场X α散射波分子轨道方法对含4、9和15个原子的铁团簇进行了计算。对散装铁的值的几个属性的收敛性进行了研究。磁性效应对电子结构的主导作用很快建立起来，甚至四原子团簇也显示出大块铁的大交换分裂和高磁矩特性。其他一些量，如d-，特别是s-带宽，收敛得更慢。对于Fe 15，体密度态（DOS）的所有主要特征都存在于团簇DOS中。的DOS峰的能量位置是足够接近的散装铁，在散装铁的约束力的定性讨论，可以给出在集群波函数的性质。自旋密度图已产生的Fe 15和这些承担一个惊人的相似之处，来自散装铁的中子散射实验。计算了接触超精细场的值，对于外围原子，发现与能带理论和实验结果的合理一致性。实验观察到的铁的磁矩在高温下的增加是合理化的基础上的集群计算Fe 15。虽然人们能够通过检查Fe 15的性质来深入了解大块铁的性质，但由于簇的有限大小，也存在一些明显的差异。中心原子有一个大约为1的多余负电荷，而这些额外的电荷大部分是少数自旋，导致磁矩比周围原子的磁矩小得多。在中心原子的局域态密度也是非典型的自旋密度的详细形式和接触超精细场的值。总的来说，外围原子比中心原子更像块状，尽管它们缺少一些最近的邻居。非自旋极化的计算Fe 15导致更好地理解为什么铁是铁磁性通过斯通类型的分析。对于顺磁性Fe 15的费米能级位于非常接近的DOS的整体最大值。此外，在ε F处的团簇波函数是反键的，因此在空间中高度局域化，这将导致团簇的”Stoner积分“的大值。“因此，顺磁性铁的不稳定性在量子化学概念方面得到了合理化。
Self-consistent-field X α-scattered-wave molecular-orbital calculations have been performed for iron clusters containing four, nine, and fifteen atoms. The convergence of several properties toward the values for bulk iron has been examined. The dominance of magnetic effects on the electronic structure is quickly established; even the four-atom cluster displays the large exchange splitting and high magnetic moment characteristic of bulk iron. Some other quantities, such as the d-and especially the s-band width, converge more slowly. For Fe 15 all of the major features of the bulk density of states (DOS) are present in the cluster DOS. The energy positions of the DOS peaks are sufficiently near those of bulk iron that a qualitative discussion of the binding in bulk iron may be given in terms of the nature of the cluster wave functions. Spin-density maps have been generated for Fe 15 and these bear a striking resemblance to those derived from neutron scattering experiments on bulk iron. Values of the contact hyperfine field have been calculated and, for the peripheral atoms, reasonable agreement with band theory and with experimental results is found. The experimentally observed increase in the magnetic moment of iron at high temperature is rationalized on the basis of the cluster calculation for Fe 15. While one is able to obtain much insight into the properties of bulk iron by examining those of Fe 15, there are also some clear differences due to the finite size of the cluster. The central atom has an excess negative charge of about one, and most of this extra charge is of minority spin, leading to a magnetic moment which is much smaller than those for the peripheral atoms. The local density of states at the central atom is also atypical as is the detailed form of the spin density and the value of the contact hyperfine field. Overall the peripheral atoms are more bulklike than the central atom despite the fact that they are missing some nearest neighbors. Non-spinpolarized calculations for Fe 15 lead to a better understanding of why iron is ferromagnetic through a Stoner-type analysis. For paramagnetic Fe 15 the Fermi level is situated very near the overall maximum of the DOS. Moreover the cluster wave functions at ε F are antibonding and hence highly localized in space, which would lead to a large value for the cluster" Stoner integral." Thus a rationalization for the instability of paramagnetic iron has been obtained in terms of quantum chemical concepts.