2013 Fiscal Year Annual Research Report
Development of first-principles computational methods for angle-resolved photoemission from organic molecules
| Project/Area Number |
25887008
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| Research Category |
Grant-in-Aid for Research Activity Start-up
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| Research Institution | Chiba University |
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Principal Investigator |
KRUEGER PETER 千葉大学, 融合科学研究科(研究院), 教授 (30706362)
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| Project Period (FY) |
2013-08-30 – 2015-03-31
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| Keywords | 物理理論 / 分子性固体 / 光物性 / 計算物理 / 光電子スペクトル |
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| Research Abstract |
The main objective of the first year was to develop a molecular orbital (MO) + multiple scattering (MS) method for angle resolved ultraviolet photoemission (ARUPS). This objective has been met. We managed to combine the output of a MO calculation for the valence states using the Gaussian software with a full multiple scattering calculation for the photoemission final state using our own MS code. Next the code has been adapted for final state potentials from overlapping atomic charge densities (POTGEN code) which improves considerably over commonly used free atom potentials. The new MO-MS method has been applied to ARUPS from a valence (4 sigma) orbital of carbon monoxide (CO) either free or adsorbed on Ni(111). The following results have been established. 1) The ARUPS spectra show a large interference between emission from C and O which is due to the delocalization of the molecular orbital over the two atoms. 2) The ARUPS pattern is very sensitive not only to the orientation of the molecule, but also to the adsorption site. Indeed the azimuthal variation of the photoelectron pattern is largely determined by the substrate confirming the direct qualtitative interpretation of the experimental data. This result clearly shows that ARUPS can be used to study the molecule-substrate interface. ARUPS gives information not only about molecular orientation and band structure, but also on the adsorption site and the details of the molecule-to-substrate bonding. Our results on CO/Ni(111) show that such information can be extracted by comparing experimental data with MO-MS calculations.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The main objective of the first year has been met. The MO-MS method is working and was successfully tested on simple systems (free CO and CO/Ni(111)).
However, with respect to the initial plan, we are somewhat behind schedule, because the implementation of two-center integrals for more accurate transition matrix elements (and thus more accurate photoemission intensities) is not finished yet.
The main reason is probably that I could not spend as much time as I wanted on the project, because in my new position I had to prepare several new lectures, and I have set up a research group with only Bachelor students. Unfortunately, the training of a Bachelor student costs more time than it gives back through his contribution to the research project (in the first year).
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| Strategy for Future Research Activity |
The research project will be pursued as planned.
After finishing the development of the MO-MS method, it will be applied to the system Sn-phthalocyanine adsorbed on Ag(111) in order to understand the change of molecule-substrate bonding between the two switching states (Sn-up and Sn-down).
Next the all-MS (multiple scattering) method will be developed along the following 3 steps. 1) Calculation of a precise, all-electron crystal potential from charge densities obtained with the plane-wave code VASP, by solving the Poisson equation in the atomic cells. 2) Calculation of T-matrices for non-spherical atomic cells. 3) Computation of the transition matrix elements.
Finally, the all-MS method will be applied to the same systems previously studied using MO-MS, especially CO/Ni(111) and Sn-phthalocyanine/Ag(111) in order to asses the accuracy, complementarity and performance of the two methods.
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