First principles calculations of the structure and V L-edge X-ray absorption spectra of V2O5 using local pair natural orbital coupled cluster theory and spin-orbit coupled configuration interaction approaches
First principles calculations of the structure and V L-edge X-ray absorption spectra of V2O5 using local pair natural orbital coupled cluster theory and spin-orbit coupled configuration interaction approaches
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DOI：
10.1039/c3cp50709b
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发表时间：
2013-01-01
影响因子：
3.3
通讯作者：
Neese, Frank
中科院分区：
文献类型：
--
作者：
Maganas, Dimitrios;Roemelt, Michael;Neese, Frank
详细研究了V2O5的电子结构和几何结构及其x射线光谱特性。为了表示V2O5的表面和体环境，构建了尺寸逐渐增大的簇模型。这些模型在边缘处或嵌入马德隆场中以氢原子终止。采用色散校正的局域、杂化和双杂化密度泛函理论以及局域对自然轨道耦合簇法（LPNO-CCSD）研究了其结构和层间结合能。通过将模型扩展到20个钒中心，结果与簇大小趋同。基于新开发的限制开壳组态与单分子相互作用（DFT-ROCIS）方法，计算了V2O5的O - k边缘和V - L-2、l -3边缘的NEXAFS光谱。在本研究中，将该方法的适用性扩展到固态催化领域。首次实现了V2O5钒l边NEXAFS光谱的理论预测与实验测量的极好一致性。同时，氧k边谱的理论与实验结果吻合良好。重要的是，氧k边和钒l边光谱之间的强度分布得到了正确的再现，从而表明计算正确地描述了金属-配体键的共价。采用准原子jj耦合和分子LS耦合两种方案，从电子结构的角度讨论了光谱特征的来源。研究了由弱层间相互作用驱动的体环境的影响，表明为了正确计算固体中的核心能级吸收光谱，大簇是重要的。
A detailed study of the electronic and geometric structure of V2O5 and its X-ray spectroscopic properties is presented. Cluster models of increasing size were constructed in order to represent the surface and the bulk environment of V2O5. The models were terminated with hydrogen atoms at the edges or embedded in a Madelung field. The structure and interlayer binding energies were studied with dispersion-corrected local, hybrid and double hybrid density functional theory as well as the local pair natural orbital coupled cluster method (LPNO-CCSD). Convergence of the results with respect to cluster size was achieved by extending the model to up to 20 vanadium centers. The O K-edge and the V L-2,L-3-edge NEXAFS spectra of V2O5 were calculated on the basis of the newly developed Restricted Open shell Configuration Interaction with Singles (DFT-ROCIS) method. In this study the applicability of the method is extended to the field of solid-state catalysis. For the first time excellent agreement between theoretically predicted and experimentally measured vanadium L-edge NEXAFS spectra of V2O5 was achieved. At the same time the agreement between experimental and theoretical oxygen K-edge spectra is also excellent. Importantly, the intensity distribution between the oxygen K-edge and vanadium L-edge spectra is correctly reproduced, thus indicating that the covalency of the metal-ligand bonds is correctly described by the calculations. The origin of the spectral features is discussed in terms of the electronic structure using both quasi-atomic jj coupling and molecular LS coupling schemes. The effects of the bulk environment driven by weak interlayer interactions were also studied, demonstrating that large clusters are important in order to correctly calculate core level absorption spectra in solids.