Seoul National University · Materials Science
Professor YounJoon Jung's research lab specializes in computational materials science and molecular simulations, focusing on the fundamental properties and behaviors of advanced nanomaterials and electrolyte systems. Key research directions include understanding ion dynamics and charge transport in supercooled liquids and ionic liquids, exploring the structural and electronic properties of two-dimensional transition-metal dichalcogenides—particularly PtSe₂—with a focus on thickness-dependent metal–semiconductor transitions, and developing machine learning models for predicting solvation thermodynamics in diverse solvents. The lab integrates molecular dynamics simulations with theoretical frameworks such as dynamical facilitation and quantitative structure-property relationship (QSPR) modeling to address challenges in energy storage, 2D electronics, and molecular solvation.
Figures are computed from collected data and may differ slightly.
By applying the concept of dynamical facilitation and analyzing the excitation lines that result from this facilitation, we investigate the origin of decoupling of transport coefficients in supercooled liquids. We illustrate our approach with two classes of models. One depicts diffusion in a strong glass former, and the other in a fragile glass former. At low temperatures, both models exhibit violation of the Stokes-Einstein relation, $D\ensuremath{\sim}{\ensuremath{\tau}}^{\ensuremath{-}1}$, wh
Two-dimensional (2D) transition-metal dichalcogenides (2D TMDs) in the form of MX<sub>2</sub> (M: transition metal, X: chalcogen) exhibit intrinsically anisotropic layered crystallinity wherein their material properties are determined by constituting M and X elements. 2D platinum diselenide (2D PtSe<sub>2</sub>) is a relatively unexplored class of 2D TMDs with noble-metal Pt as M, offering distinct advantages over conventional 2D TMDs such as higher carrier mobility and lower growth temperatures
Supercapacitors with two single-sheet graphene electrodes in the parallel plate geometry are studied via molecular dynamics (MD) computer simulations. Pure 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI+BF4-) and a 1.1 M solution of EMI+BF4- in acetonitrile are considered as prototypes of room-temperature ionic liquids (RTILs) and organic electrolytes. Electrolyte structure, charge density and associated electric potential are investigated by varying the charges and separation of the two ele
We investigate the charging phenomena of an electric double layer capacitor (EDLC) by conducting both equilibrium and non-equilibrium molecular dynamics (MD) simulations. A graphene electrode and 1-ethyl-3-methylimidazolium thiocyanate ([EMIM]+[SCN]-) ionic liquid were used as a system for the EDLC. We clarify the ionic layer structure and show that an abrupt change of the ionic layers leads to a high differential capacitance of the EDLC. The charging simulations reveal that the charging dynamic
Prediction of aqueous solubilities or hydration free energies is an extensively studied area in machine learning applications in chemistry since water is the sole solvent in the living system. However, for non-aqueous solutions, few machine learning studies have been undertaken so far despite the fact that the solvation mechanism plays an important role in various chemical reactions. Here, we introduce <i>Delfos</i> (deep learning model for solvation free energies in generic organic solvents), w
Diffusion of long ring polymers in a melt is much slower than the reorganization of their internal structures. While direct evidence for entanglements has not been observed in the long ring polymers unlike linear polymer melts, threading between the rings is suspected to be the main reason for slowing down of ring polymer diffusion. It is, however, difficult to define the threading configuration between two rings because the rings have no chain end. In this work, evidence for threading dynamics
Platinum diselenide (PtSe<sub>2</sub>) is an emerging class of two-dimensional (2D) transition-metal dichalcogenide (TMD) crystals recently gaining substantial interest, owing to its extraordinary properties absent in conventional 2D TMD layers. Most interestingly, it exhibits a thickness-dependent semiconducting-to-metallic transition, i.e., thick 2D PtSe<sub>2</sub> layers, which are intrinsically metallic, become semiconducting with their thickness reduced below a certain point. Realizing bot
We survey the current status of single-molecule spectroscopy in the view point of theoretical aspects. After an explanation of basic concepts in single-molecule spectroscopy, we focus on the following topics: (1) line shape phenomena in disordered media, (2) photon counting statistics for time-dependent fluctuations in single-molecule spectroscopy, (3) fluorescence intensity fluctuations for nonergodic systems, (4) time-resolved single-molecule fluorescence for conformational dynamics of single
Dynamics of a coarse-grained model for the room-temperature ionic liquid, 1-ethyl-3-methylimidazolium hexafluorophosphate, couched in the united-atom site representation are studied via molecular dynamics simulations. The dynamically heterogeneous behavior of the model resembles that of fragile supercooled liquids. At or close to room temperature, the model ionic liquid exhibits slow dynamics, characterized by nonexponential structural relaxation and subdiffusive behavior. The structural relaxat
Two-dimensional (2D) molybdenum disulfide (MoS<sub>2</sub>) with vertically aligned (VA) layers exhibits significantly enriched surface-exposed edge sites with an abundance of dangling bonds owing to its intrinsic crystallographic anisotropy. Such structural variation renders the material with exceptionally high chemical reactivity and chemisorption ability, making it particularly attractive for high-performance electrochemical sensing. This superior property can be further promoted as far as it
Abstract Heterogeneously integrated 2D van der Waals (vdW) solids composed of compositionally distinct atomic layers are envisioned to exhibit exotic electrical/optical properties unattainable with their monocomponent counterparts. However, the underlying principle for their morphology‐controlled chemical vapor deposition (CVD) growth and its associated growth variables have not been clarified, leaving their projected technological opportunities far from being realized. Herein, by employing tung
Redox-active organic materials (ROMs) hold great promise as potential electrode materials for eco-friendly, cost-effective, and sustainable batteries; however, the poor cycle stability arising from the chronic dissolution issue of the ROMs in generic battery systems has impeded their practical employment. Herein, we present that a rational selection of electrolytes considering the solubility tendency can unlock the hidden full redox capability of the DMPZ electrode (i.e., 5,10-dihydro-5,10-dimet
It is necessary to quantitatively determine substituent effects to accurately elucidate reaction mechanisms in the field of organic chemistry. This paper reports that the molecular electrostatic potential (MESP) can be used as a general and versatile measure for the substituent effects in various chemical reactions by performing extensive density functional theory (DFT) calculations for more than 400 molecules, followed by statistical analyses. We observed a robust and linear correlation between
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