Min, Seung Kyu

Min, Seung Kyu

Min, Seung Kyu 민승규
Assistant Professor

The electron-nuclear correlation plays a major role in dynamial processes like a chemical reaction with an extra energy and the light-matter interaction. Such cases are called as excited state phenomena which are actually ubiquitous in nature like vision process and photosynthesis. In our research group, we are interested in the theoretical/computational description of excited state phenomena and its applications with following questions:

(a) How can we describe correlated electron-nuclear motions correctly?
(b) How can we deal with chemical reactions in the excited states theoretically?
(c) Based on our knowledge, how can we design functional molecular devices such as energy materials, nano-electronic/photonic devices?

So far we have achieved several things. First, we have developed a novel efficient numerical algorithm for excited state dynamics with multiple "interacting" classical trajectories. This original method outperforms the conventional approaches in a sense that it can describe the exact nuclear dynamics in the excited states as well as the correct electronic dynamics. Currently we focus on understanding chemical dynamics on excited states (such as photosynthesis and vision process) and designing novel molecular functional devices based on our approach.
Research Summary
My research group aims to describe excited state phenomena of molecules and materials, based on understanding of electron-nuclear correlation, as following:

(a) Calculation of excitation energies and Born-Oppenheimer potential energy surfaces, and prediction of chemical reaction on excited states
(b) Calculation of optical properties of a molecules and interesting materials
(c) Development of a novel algorithm for excited state dynamics
(d) Development of molecular functional devices such as molecular machines, molecular photonic devices, solar cells and so on based on optical/dynamical properties of molecules.

Excited state potential energy surfaces contain a large number of coupling region between adiabatic states, namely “non-adiabatic coupling region” such as conical intersections and avoided crossing, due to the electron-nuclear correlation. Many interesting excited state phenomena (ultrafast relaxation of molecules, radiationless decay, electron transfer, exciton energy transfer, etc…) are highly related to non-adiabatic behavior of potential energy surfaces. Therefore, the theoretical description of the correct electron-nuclear correlation is crucial for the excited state phenomena. Based on the study of electron-nuclear correlation, we develop a novel algorithm for coupled electron-nuclear dynamics on excited states. Finally we predict interesting optical properties of excited molecules based on the implementation of our approach to ab initio program package.

본 연구실에서는 새롭게 개발된 들뜬 상태 동역학 방법을 바탕으로 다음과 같이 실제 분자와 빛의 상호작용과 관련된 현상을 이론적으로 연구한다.

(1) 들뜬 상태 에너지 계산 및 포텐셜 표면을 이용한 화학반응의 예측
(2) 물질의 광학적 성질 계산
(3) 원자핵과 전자의 상관 현상 구현을 위한 새로운 반응 동역학 알고리즘 구현
(4) 들뜬 상태 동역학 연구를 통한 태양 전지, 분자 광 소자 등 새로운 분자 소자의 개발 및 물성 예측

들뜬 상태의 포텐셜 에너지 표면은 conical intersection과 avoided crossing과 같이 “non-adiabatic coupling region”이라 불리는 다수 존재하는데, 이러한 non-adiabatic 현상은 특정 분자 구조에서 원자핵의 움직임과 전자의 움직임이 밀접하게 연관되어 있기 때문에 나타난다. ultrafast relaxation of molecules, 전자 전달, 들뜬 상태 에너지 전달 등 흥미로운 들뜬 상태 현상은 대부분 앞서의 포텐셜 에너지 표면의 non-adiabatic 성질과 연관이 되어있다고 알려져 있으며, 따라서 들뜬 상태 현상을 이론적으로 이해하기 위해서는 전자와 원자의 상관 현상을 제대로 기술할 수 있는 방법론이 우선시 개발되어야 한다. 이에 본 연구실에서는 전자-원자간 상관 현상 연구를 바탕으로 새로운 들뜬 상태 동역학 알고리즘을 개발하고, 제 1원리 계산과 결합하여 들뜬 분자에서 일어나는 흥미로운 광학적인 현상을 예측하며, 이를 바탕으로 새로운 분자 소자를 디자인한다.

Representative Publications
"Is the molecular Berry phase an artifact of Born-Oppenheimer approximation?"
S. K. Min, A. Abedi, K. S. Kim, E. K. U. Gross, Phys. Rev. Lett. 113, 263004 (2014)

"Coupled-trajectory quantum-classical approach to electronic decoherence in nonadiabatic processes"
S. K. Min, F. Agostini, E. K. U. Gross, Phys. Rev. Lett., 115, 073001 (2015)

"Fast DNA sequencing with a graphene-based nanochannel device"
S. K. Min, W. Y. Kim, Y. Cho, K. S. Kim, Nature Nanotechnol, 6, 162 (2011)

"Efficient electron dynamics with the plane wave-based realtime time-dependent density functional theory: absorption spectra, vibronic electronic spectra, and coupled electron-nucleus dynamics"
S. K. Min, Y. Cho, K. S. Kim, J. Chem. Phys., 135, 244112 (2011)