Kuusik I, Berholts M, Kruusma J, Kisand V, Tõnisoo A, Lust E, Nõmmiste E
Institute of Physics, University of Tartu W. Ostwaldi 1 50411 Tartu Estonia.
Dept. of Physics and Astronomy, University of Turku FIN-20014 Turku Finland.
RSC Adv. 2018 Aug 28;8(53):30298-30304. doi: 10.1039/c8ra05865b. eCollection 2018 Aug 24.
The ultraviolet photoelectron spectrum (UPS) of the [EMIM][BF] ionic liquid was recorded and analyzed. Together with the gas-phase UPS spectrum of the [EMIM][BF] vapor and calculation methods, detailed insight into the electronic structure of this simple ionic liquid is possible. The low binding energy tail in the UPS spectrum is about 7.4 eV, in agreement with previous estimations of the HOMO-LUMO gap of the [EMIM][BF] ion-pair. The bulk calculations are able to explain most of the features in the spectrum. However, DFT consistently lacks accuracy in the description of the top of the valence band. The dispersion corrected PBE calculation (PBE-D3) did offer very good agreement with the experimental structure, but the recently-developed vdW-DF functionals C09, optPBE, optB88 and CX were found to offer the best agreement in terms of the electronic structure.
记录并分析了[EMIM][BF]离子液体的紫外光电子能谱（UPS）。结合[EMIM][BF]蒸气的气相UPS能谱和计算方法，能够深入了解这种简单离子液体的电子结构。UPS能谱中低结合能尾部约为7.4 eV，这与之前对[EMIM][BF]离子对的最高占据分子轨道（HOMO）-最低未占据分子轨道（LUMO）能隙的估计一致。体相计算能够解释能谱中的大部分特征。然而，密度泛函理论（DFT）在价带顶的描述上始终缺乏准确性。色散校正的PBE计算（PBE-D3）与实验结构确实吻合得很好，但发现最近开发的范德华密度泛函C09、optPBE、optB88和CX在电子结构方面的吻合度最佳。
