Evaluation of 27Al and 51V electric field gradients and the crystal structure for aluminum orthovanadate (AlVO4) by density functional theory calculations
Evaluation of 27Al and 51V electric field gradients and the crystal structure for aluminum orthovanadate (AlVO4) by density functional theory calculations
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DOI：
10.1021/jp0555549
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发表时间：
2006-03-30
影响因子：
3.3
通讯作者：
Skibsted, J
中科院分区：
文献类型：
--
作者：
Hansen, MR;Madsen, GKH;Skibsted, J
采用维也纳从头算模拟软件包（VASP），对AIVO（4）的三组晶体结构数据进行了研究，并使用WIEN 2k软件中的密度泛函理论（DFT）结构优化方案进行了优化。最近报道的Al-27和V-51四极耦合参数的基础上，AlVO 4的晶体结构进行评估，采用相应的电场梯度（EFG）张量元素从DFT计算得到的。DFT计算提供了一个可靠的分配的Al-27/V-51共振从三个不同的Al和三个V的环境中的特定的结晶位点的不对称单元的AlVO 4。通过对三种不同结构的DFT结构进行优化，得到了一致的结果，实验四极张量元和计算EFG张量之间的一致性得到了改善。DFT结构优化前后的Al-O和V-O键长的评价也支持结构数据的改进。V-51核四极矩，垂直条Q（V-51）垂直条= 4.8 +/- 0.1 fm（2），从本分析中得出，代表了比早期报道的Q（V-51）值更高的准确度值。的Al-27和V-51 EFG的起源进行了调查的EFG张量在晶体框架中的取向的评价和检查的个别贡献的价电子和周围的晶格。后者的研究表明，张量的大小和取向主要取决于p-p（Al-27）和p-p，d-d（V-51）轨道对价电子的贡献，而晶格部分仅对两个核的贡献很小。
Three sets of crystal-structure data reported for AIVO(4) from two powder-XRD studies and a density functional theory (DFT) investigation, employing the Vienna ab initio simulation package (VASP), have been examined and refined using the DFT structure-optimization scheme implemented in the WIEN2k software. The crystal structures are evaluated on the basis of Al-27 and V-51 quadrupole coupling parameters recently reported for AIVO4, employing the corresponding electric-field gradient (EFG) tensor elements obtained from the DFT calculations. The DFT calculations provide a reliable assignment of the Al-27/V-51 resonances from three distinct Al and three V environments to the specific crystallographic sites in the asymmetric unit for AIVO4. An improved agreement between experimental quadrupole tensor elements and calculated EFG tensors is achieved after the DFT structure optimizations and consistent results are obtained using the three different structures as starting points. The improvement of the structural data is also supported by an evaluation of the Al-O and V-O bond lengths before and after DFT structure optimization. The V-51 nuclear quadrupole moment, vertical bar Q(V-51)vertical bar = 4.8 +/- 0.1 fm(2), derived from the present analysis, represents a value of higher accuracy than earlier reported Q(V-51) values. The origin of the Al-27 and V-51 EFGs are investigated by an evaluation of the orientations of the EFG tensors in the crystal frame and by an examination of the individual contributions from the valence electrons and the surrounding lattice. The latter investigation shows that the magnitude and orientation of the tensors are largely determined by the p-p(Al-27) and p-p, d-d(V-51) orbital contributions to the valence electrons, while the lattice part only gives a minor contribution for both nuclei.