Kwang S. Kim

Bio: Kwang S. Kim is an academic researcher from Ulsan National Institute of Science and Technology. The author has contributed to research in topics: Ab initio & Graphene. The author has an hindex of 97, co-authored 642 publications receiving 62053 citations. Previous affiliations of Kwang S. Kim include Asia Pacific Center for Theoretical Physics & IBM.

Structures, energetics, and spectra of aqua-sodium(i) : thermodynamic effects and nonadditive interactions

Abstract: Using extensive ab initio calculations including electron correlation, we have studied structures, thermodynamic quantities, and spectra of hydrated sodium ions [Na(H2O)+n (n=1–6)] Various configurations were investigated to find the stable structures of the clusters The vibrational frequency shifts depending on the number of water molecules were investigated along with the frequency characteristics depending on the presence/absence of outer‐shell water molecules The thermodynamic quantities of the stable structures were compared with experimental data available Entropy‐driven structures for n=5 and particularly for n=6 are noted in the calculations, which can explain the peculiar experimental thermal energies On the other hand, the enthalpy effect to maximize the number of hydrogen bonds of the clusters with the surrounding water molecules seems to be the dominant factor to determine the primary hydration number of Na+ in aqueous solution The nonadditive interactions in the clusters are found to be

Induction‐Driven Stabilization of the Anion–π Interaction in Electron‐Rich Aromatics as the Key to Fluoride Inclusion in Imidazolium‐Cage Receptors

Abstract: Intermolecular interactions that involve aromatic rings are key pro- cesses in both chemical and biological recognition. It is common knowledge that the existence of anion-p interac- tions between anions and electron-defi- cient (p-acidic) aromatics indicates that electron-rich (p-basic) aromatics are expected to be repulsive to anions due to their electron-donating character. Here we report the first concrete theo- retical and experimental evidence of the anion-p interaction between elec- tron-rich alkylbenzene rings and a fluo- ride ion in CH3CN. The cyclophane cavity bridged with three naphthoimi- dazolium groups selectively complexes a fluoride ion by means of a combina- tion of anion-p interactions and (C H) + ···F-type ionic hydrogen bonds. 1 H NMR, 19 F NMR, and fluorescence spectra of 1 and 2 with fluoride ions are examined to show that only 2 can host a fluoride ion in the cavity be- tween two alkylbenzene rings to form a sandwich complex. In addition, the cage compounds can serve as highly se- lective and ratiometric fluorescent sen- sors for a fluoride ion. With the addi- tion of 1 equiv of F, a strongly in- creased fluorescence emission centered at 385 nm appears at the expense of the fluorescence emission of 2 centered at 474 nm. Finally, isothermal titration calorimetry (ITC) experiments were performed to obtain the binding con- stants of the compounds 1 and 2 with F as well as Gibbs free energy. The 2- F complex is more stable than the 1- F complex by 1.87 kcal mol 1 , which is attributable to the stronger anion-p in- teraction between F and triethylben- zene.

Insights into the Structures, Energetics, and Vibrations of Monovalent Cation-(Water)1-6 Clusters †

Abstract: This study details the interactions prevailing in aqueous clusters of monovalent alkali metal, ammonium, and hydronium cations. The calculations involve a detailed evaluation of the structures, thermodynamic energies, andIR spectra of several plausible conformers of M + .(H 2 O) 1 - 6 (M = Li, Na, K, Rb, Cs, NH 4 , H 3 O) clusters at the second-order Miller-Plesset (MP2) and density functional levels of theory. A detailed decomposition of the interaction energies has been carried out for complexes involving one or two water molecules using symmetry adapted perturbation theory. Some of the salient insights on the structures include the emergence of the second solvent shell even before the realization of the maximal coordination number of the cation. This effect was more pronounced in clusters involving the larger cations. The quantitative estimates of various components of the interaction energy indicate the predominance of electrostatic energies in the binding of these cations to water molecules. Interestingly, for all the hydrated alkali metal cation complexes, the contribution of electrostatic energy is almost the same as the total attractive interaction energy, whereas the sum of the induction and dispersion energies are almost canceled out by exchange-repulsion energy. However, the contribution of dispersion energies slowly starts increasing as the size of the cation increases and is quite substantial in case of the Cs + complexes. In the organic cations, the dispersion energies become significant, though not comparable to the electrostatic energies. In addition to the evaluation of the harmonic frequencies of -OH stretching mode of all the structures, the anharmonic frequencies were evaluated for the smaller clusters. As the size of the cation and the size of the water cluster increases, the red shifts associated with the -OH stretching mode progressively become larger for the alkali metal cation containing complexes. For the organic cation (NH 4 +, H 3 O + ) containing complexes, an opposite trend is observed. Compared to the isolated water monomer, the ratio of the infrared intensities of the asymmetric and symmetric -OH stretching modes is very small. However, this ratio progressively becomes larger as the size of the cation increases.

Graphene-nanoplatelets-supported NiFe-MOF: high-efficiency and ultra-stable oxygen electrodes for sustained alkaline anion exchange membrane water electrolysis

Abstract: Practical hydrogen production using high-efficiency, low-cost, and stable oxygen electrodes is crucial for a sustainable clean energy future. Herein we report a graphene-nanoplatelets-supported (Ni,Fe) metal–organic framework (MOF) as a superior and ultra-durable (>1000 h) anode for alkaline water electrolysis. The MOF on carbon-fiber paper electrodes requires an overpotential η = 220 mV to achieve a current density j = 10 mA cm−2 (η = 180 mV on nickel foam for j = 20 mA cm−2) with a Tafel slope of 51 mV per decade, high turnover frequency (1.22 s−1), high faradaic efficiency (99.1%), and long-term durability of >1000 h in continuous electrolysis. In an alkaline anion exchange membrane water electrolyzer (AAEMWE), it exhibits a record current density of 540 mA cm−2 at 1.85 V at 70 °C, outperforming the state-of-the-art Pt/C//IrO2. A breakthrough strategy introduced in membrane electrode assembly fabrication by extending the electrical contact with an aqueous electrolyte offers an additional OH− transport pathway to regenerate the original conductivity of the AAEMWE in continuous electrolysis, without any significant change in the pH of the electrolyte. These findings open up durable, high-performance AAEMWE and direct solar-to-fuel conversion, especially to replace high-cost proton exchange membrane water electrolysis that already works with ultra-pure water.

Ambipolar Memory Devices Based on Reduced Graphene Oxide and Nanoparticles

Abstract: [*] Prof. S. Hong, S. Myung, H. Lee Department of Physics and Astronomy, Seoul National University Seoul 151-747 (Korea) Department of Biophysics and Chemical Biology, Seoul National University Seoul 151-747 (Korea) E-mail: shong@phya.snu.ac.kr Prof. K. S. Kim, J. Park Center for Superfunctional Materials, Department of Chemistry Pohang University of Science and Technology Pohang 790-784 (Korea) E-mail: kim@postech.ac.kr

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials

Abstract: QUANTUM ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, and pseudopotentials (norm-conserving, ultrasoft, and projector-augmented wave). The acronym ESPRESSO stands for opEn Source Package for Research in Electronic Structure, Simulation, and Optimization. It is freely available to researchers around the world under the terms of the GNU General Public License. QUANTUM ESPRESSO builds upon newly-restructured electronic-structure codes that have been developed and tested by some of the original authors of novel electronic-structure algorithms and applied in the last twenty years by some of the leading materials modeling groups worldwide. Innovation and efficiency are still its main focus, with special attention paid to massively parallel architectures, and a great effort being devoted to user friendliness. QUANTUM ESPRESSO is evolving towards a distribution of independent and interoperable codes in the spirit of an open-source project, where researchers active in the field of electronic-structure calculations are encouraged to participate in the project by contributing their own codes or by implementing their own ideas into existing codes.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。