| 研究課題/領域番号 |
19K15397
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| 研究機関 | 東京大学 |
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研究代表者 |
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| 研究期間 (年度) |
2019-04-01 – 2024-03-31
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| キーワード | nanostructure / nanojunction / ortho-para / hydrogen / DFT / NEGF / anisotropic / molecule |
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| 研究実績の概要 |
This year, the rotational effects of H2 molecule in a nanojunction was investigated by means of model Hamiltonian calculations. The adsorption and interaction parameters were obtained from first principles calculations based on the density functional theory. The orientation-dependent current was calculated using NEGF formalism. Ihe vibrational effects is also incorporated through the electron-phonon coupling. Our results recovered the previously understood electron-phonon effects in the quantum dot system where step-like features in the current and periodic peaks in the conductance are attributed to the Frank-Condon excitations. We also derived an expression for the interaction between the metal junctions and H2 at a microscopic level accounting for the orientation of the molecule with respect to the junctions. We found that the current is suppressed when the molecular orientation is parallel to the surfaces of the metals. Further, the spectral function (SF) at this orientation narrows indicating the reduction of the electron hopping between the junction and H2.
This strong orientation effects can be similarly seen in the rotational averaged SF and current. The J=0,m=0 (para) SF is narrow compared to J=1,m=0 (ortho). The J=1,m=1 SF is narrowest among the rotational states investigated. In the gas phase, J=1,m=0 and J=1,m=1 states are degenerate in energy and both SF of these states are expected to be the similar. The electronic interaction between the metal junctions and H2 cause the splitting of these states and results in anisotropic current in the nanojunction.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
The model calculations for ortho-para conversion as well as the NEGF calculations for anisotropic current in a nanojunction have been developed and the computation could proceed smoothly. The parameters from both these calculations were obtained directly from DFT calculations without much difficulty. The construction of potential energy surfaces (PES) using neural network potential (NNP) remains challenging due to the parameters involved in the training.
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| 今後の研究の推進方策 |
In the future, the construction of potential energy surfaces (PES) using neural network potential (NNP) will be continued and improved. From this PES, the adsorption potential energy for different chemical potentials of H2 will be obtained. Furthermore, quantum effects such as tunneling and zero-point energies will be incorporated to derive a complete picture of hydrogen adsorption in nanostructures.
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| 次年度使用額が生じた理由 |
Although the situation regarding the pandemic is gradually improving, conferences of some academic societies remained online this year. I was able to attend two conferences abroad and plans to attend another one this year. The remaining amount will be used to purchase books and computing materials.
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