First-principles multielectron calculations of Ni L2,3 NEXAFS and ELNES for LiNiO2 and related compounds -: art. no. 075123
First-principles multielectron calculations of Ni L2,3 NEXAFS and ELNES for LiNiO2 and related compounds -: art. no. 075123
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DOI：
10.1103/physrevb.72.075123
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发表时间：
2005-08-01
影响因子：
3.7
通讯作者：
Ogasawara, K
中科院分区：
文献类型：
--
作者：
Ikeno, H;Tanaka, I;Ogasawara, K
采用三维过渡金属L-2、L-3边近边X射线吸收精细结构(NEXAFS)和电子能量损失近边结构(ELNES)技术对NiO、LiNiO_2和NiO_2的光谱进行了预测和解释。多电子波函数由斯莱特行列式的线性组合得到。斯莱特行列式是使用所有基于Ni-2p和Ni-3d的分子轨道，而不是原子轨道，通过在NiO6m-团簇(m=10，9和8)的局域密度近似下求解Dirac方程而得到的。因此，通过共价的O-2p贡献可以在没有任何其他方案的情况下自动包括在内。实验结果表明，Ni原子在LiNiO2中为低自旋态的Ni(III)，在NiO2中为低自旋态的Ni(IV)。还阐明了光谱中卫星峰的来源。该方法基于稳健的多电子量子理论，可用于其他过渡金属化合物的L-2、L-3边谱的分析和预测。
A technique to compute 3d transition-metal L-2,L-3-edge near-edge x-ray-absorption fine structure (NEXAFS) and electron energy-loss near-edge structure (ELNES) is adopted to predict and interpret spectra from NiO, LiNiO2, and NiO2. Multielectron wave functions were obtained as a linear combination of Slater determinants. The Slater determinants were constructed using all Ni-2p- and Ni-3d-based molecular orbitals, instead of atomic orbitals, obtained by solving the Dirac equation within the local density approximation for NiO6m- clusters (m=10, 9, and 8). The O-2p contributions through covalency can therefore be included automatically without any other scheme. Experimental ELNES for the three compounds were satisfactory reproduced by the present calculations, which unambiguously shows that Ni atoms are Ni(III) with a low-spin state in LiNiO2, and Ni(IV) with a low-spin state in NiO2. The origin of satellite peaks in the spectra is also clarified. The present method is based on the robust multielectron quantum theory, which could be applied to the analysis and prediction of L-2,L-3-edge spectra of other transition-metal compounds.