用密度泛函理论研究稀土元素HCP和BCC基态及XPS和BIS的f能级行为
The behavior of f-levels in HCP and BCC rare-earth elements in the ground state and in XPS and BIS spectroscopy from density-functional theory
摘要：
用密度泛函理论计算了稀土元素的HCP结构和铕的BCC结构的电子结构。在DFT中模拟X射线光电子能谱（XPS）和韧致辐射等色谱（BIS），其中f电子被大光子能量激发，或者从XPS中的占据态中移除，或者加入BIS中的未占据f态。结果表明，f-态的表观位置与基态的f-带能量相比存在相当大的差异。这个结果是从根本上不同的计算假设强现场相关，因为所有的计算是基于DFT。自旋轨道耦合和多重态分裂不包括在内。目前的模拟占了几乎一半的DFT基态中的f-能级位置和观察到的f-能级位置之间的差异。在低T下的电子比热与DFT基态相容，其中f电子通常驻留在费米能级。
英文摘要：
The electronic structures of rare-earth elements in the HCP structure, and Europium in the BCC structure, are calculated by use of density-functional theory, DFT. Simulation of X-ray photoemission spectroscopy (XPS) and bremsstrahlung isochromatic spectroscopy (BIS) are made within DFT by imposing that f-electrons are excited by a large photon energy, either by removing from the occupied states in XPS, or by adding to the unoccupied f-states in BIS. The results show sizable differences in the apparent position of the f-states compared to the f-band energy of the ground states. This result is fundamentally different from calculations assuming strong on-site correlation since all calculations are based on DFT. Spin-orbit coupling and multiplet splittings are not included. The present simulation accounts for almost half of the difference between the f-level positions in the DFT ground states and the observed f-level positions. The electronic specific heat at low T is compatible with the DFT ground state, where f-electrons often reside at the Fermi level.
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