Chang Woo Myung
Ulsan National Institute of Science and Technology · Materials Science
Chang Woo Myung 교수의 연구실은 에너지 재료와 나노구조 물질의 원자적 거동을 이해하고자, 밀도함수이론(DFT)과 기계학습 기반 분자역학 시뮬레이션을 융합한 고정밀 이론적 연구를 수행합니다. 주요 연구 분야는 리튬이온 배터리의 고에너지 정합성 향상, 페로브스카이트 태양전지의 전자 구조 최적화, 그리고 초고압 상태에서의 양자물질 상전이 등입니다. 특히, 기계학습 잠재력과 정밀한 전자구조 계산 기법을 활용해 복잡한 이종계계재료의 안정성과 기능성을 예측하는 데 초점을 맞추고 있습니다.
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Abstract The anion redox reaction in high‐energy‐density cathode materials such as Li‐excess layered oxides suffers from voltage/capacity fadings due to irreversible structural instability. Here, exploiting density functional theory (DFT) as well as fast simulations using the universal potential/forces generated from the newly developed sparse Gaussian process regression (SGPR) machine learning (ML) method, the very complicated/complex structures, X‐ray absorption near‐edge‐structure (XANES) spe
Recently, La-doped BaSnO<sub>3</sub> (LBSO) electron transport layer for perovskite solar cells has been introduced to replace TiO<sub>2</sub> which is susceptible to UV light. This paper unveils the key mechanism for the ideal band alignment between LBSO and MAPbI<sub>3</sub>. The amount of La dopant in LBSO is crucial for the fine tuning of the conduction band level of LBSO.
Abstract Metal halide perovskite (MHP) is a promising next generation energy material for various applications, such as solar cells, light emitting diodes, lasers, sensors, and transistors. MHPs show excellent mechanical, dielectric, photovoltaic, photoluminescence, and electronic properties, and such intriguing physical and chemical properties have drawn attention recently. However, there exists a chasm between the successful applications of MHPs and theoretical understandings. The difficulty a
Supersolid is a mysterious and puzzling state of matter whose possible existence has stirred a vigorous debate among physicists for over 60 years. Its elusive nature stems from the coexistence of two seemingly contradicting properties, long-range order and superfluidity. We report computational evidence of a supersolid phase of deuterium under high pressure (p>800 GPa) and low temperature (T<1.0 K). In our simulations, that are based on bosonic path integral molecular dynamics, we observe a high
Recent advancements in machine learning potentials (MLPs) have significantly impacted the fields of chemistry, physics, and biology by enabling large-scale first-principles simulations. Among different machine learning approaches, kernel-based MLPs distinguish themselves through their ability to handle small datasets, quantify uncertainties, and minimize over-fitting. Nevertheless, their extensive computational requirements present considerable challenges. To alleviate these, sparsification meth
The structure of oxide-supported metal nanoclusters plays an essential role in their sharply enhanced catalytic activity over that of bulk metals. Simulations provide the atomic-scale resolution needed to understand these systems. However, the sensitive mix of metal-metal and metal-support interactions, which govern their structure, puts stringent requirements on the method used, requiring calculations beyond standard density functional theory (DFT). The method of choice is coupled cluster theor
Abstract Traditionally, Fischer–Tropsch (FT) synthesis is performed using thermal catalysts and syngas (CO and H 2 ) under high‐pressure and high‐temperature conditions. However, this study introduces an approach that relies on FT chemistry assisted by electrochemistry, referred to here as direct electrochemical (EC) FT chemistry, under ambient conditions. A series of CH 4 , C n H 2n , and C n H 2n+2 hydrocarbons (n = 1–7) is successfully produced over gold (Au) nanoparticle‐loaded perovskite st
Excited-state molecular dynamics (ESMD) simulations near conical intersections (CIs) pose significant challenges when using machine learning potentials (MLPs). Although MLPs have gained recognition for their integration into mixed quantum-classical (MQC) methods, such as trajectory surface hopping (TSH), and their capacity to model correlated electron-nuclear dynamics efficiently, difficulties persist in managing nonadiabatic dynamics. Specifically, singularities at CIs and double-valued couplin
Closed-shell light-emitting diodes (LEDs) suffer from the internal quantum efficiency (IQE) limitation imposed by optically inactive triplet excitons. Here, an unrevealed emission mechanism of lead halide perovskites (LHPs) APbX<sub>3</sub> (A = Cs/CN<sub>2</sub> H<sub>5</sub> ; X = Cl/Br/I) that circumvents the efficiency limit of closed-shell LEDs is explored. Though efficient emission is prohibited by optically inactive J = 0 in inversion symmetric LHPs, the anharmonicity arising from stereoc
We studied the effect of finite amplitude, which was ignored in Landau&apos;s linearized theory and also studied a transition criterion between linear and nonlinear Landau damping. To adjust the finite amplitude of wave and the initial trapped electron flux J(xT0), we used particle-in-cell simulation that can uniquely modulate these parameters. We predicted on the finite amplitude of wave potential and kinetic energies; these matched the simulation exactly. Oscillation and damping rates in L
The cover image representing article 1702898 by Geunsik Lee, Kwang S. Kim and co-workers, highlights four proposed A-site cations, N2H5, NH3F, LiNH2CH3, and NH3OH for perovksite solar cells compared to conventional A-site cation Cs and CH3NH3. In a Fröhlich polaron picture, proposed A-site cations reduce coupling between photo-excited carriers (electron and hole) and lattice, thus enhancing the lifetime of carriers. This theoretical study will facilitate the synthesis of novel perovskite solar c
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