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.

Anion Binding by Electron-Deficient Arenes Based on Complementary Geometry and Charge Distribution.

Abstract: Extended electron-deficient arenes are investigated as potential neutral receptors for polyanions. Anion binds via σ interaction with extended arenes, which are composed solely of C and N ring atoms and CN substituents. As a result, the positive charge on the aromatic C is enhanced, consequently maximizing binding strength. Selectivity is achieved because different charge distributions can be obtained for target anions of a particular geometry. The halides F(-) and Cl(-) form the most stable complex with 6, while the linear N3(-) interacts most favorably with 7. The trigonal NO3(-) and tetrahedral ClO4(-) fit the 3-fold rotational axis of 6 but do not form stable complexes with 5 and 7. The Y-shaped HCOO(-) forms complexes with 4, 5, and 7, with the latter being the most stable. Thus, the anion complexes exhibit strong binding and the best geometrical fit between guest and host, reminiscent of Lego blocks.

Highly selective CO2 adsorption performance of carbazole based microporous polymers

Abstract: Non-coplanar shaped carbazole based monomers were used to synthesize microporous polycarbazole materials utilizing an inexpensive FeCl3 catalyzed reaction. The reactions proceed through direct oxidative coupling and extensive crosslinking polymerization routes. The obtained porous networks exhibit a maximum Brunauer–Emmett–Teller specific surface area of 946 m2 g−1 with a total pore volume of 0.941 cm3 g−1, and display a high carbon dioxide uptake capacity (up to 13.6 wt%) at 273 K and 1 atm. Selective adsorption of CO2 over N2 calculated using the ideal adsorbed solution theory (IAST) shows that these networks display enhanced selectivity with a maximum value of 155 at 298 K. Remarkably, in contrast to other materials, this value is significantly higher than the selectivity values (102–107) obtained at 273 K. Introduction of the electron rich carbazole structure into the aromatic system and pore geometry contribute to higher adsorption enthalpy which in turn leads to high selective adsorption values. These polymeric networks also show a high working capacity with reasonably high regenerability factors. The combination of a simple inexpensive synthesis approach and high selective adsorption make these materials potential candidates for CO2 storage, selective gas adsorption, and other environmental applications.

Towards Universal Sparse Gaussian Process Potentials: Application to Lithium Diffusivity in Superionic Conducting Solid Electrolytes

Abstract: For machine learning of interatomic potentials the sparse Gaussian process regression formalism is introduced with a data-efficient adaptive sampling algorithm. This is applied for dozens of solid electrolytes. As a showcase, experimental melting and glass-crystallization temperatures are reproduced for Li7P3S11 and an unchartered infelicitous phase is revealed with much lower Li diffusivity which should be circumvented. By hierarchical combinations of the expert models universal potentials are generated, which pave the way for modeling large-scale complexity by a combinatorial approach.

Aromatic π–π interaction mediated by a metal atom: structure and ionization of the bis(η6-benzene)chromium–benzene cluster

Abstract: Aromatic π–π interaction in the presence of a metal atom has been investigated experimentally and theoretically with the model system of bis(η6-benzene)chromium–benzene cluster (Cr(Bz)2–Bz) in which a free solvating benzene is non-covalently attached to the benzene moiety of Cr(Bz)2. One-photon mass-analyzed threshold ionization (MATI) spectroscopy and first principles calculations are employed to identify the structure of Cr(Bz)2–Bz which adopts the parallel-displaced configuration. The decrease in ionization potential for Cr(Bz)2–Bz compared with Cr(Bz)2, resulting from the increase of the cation–π stabilization energy upon ionization, is consistent with the parallel-displaced structure of the cluster. Theoretical calculations give the detailed cluster structures with associated energetics, thus revealing the nature of π–π–metal or π–π–cation interactions at the molecular level.

Plasmon nanofocusing in a dielectric hemisphere covered in tapered metal film

Abstract: We propose and analyze a new type of mechanically robust optical nanofocusing probe with minimized external environmental interference. The probe consists of a dielectric optical fiber terminated by a dielectric hemisphere – both covered in thin gold film whose thickness is reduced (tapered) along the surface of the hemisphere toward its tip. Thus the proposed probe combines the advantages of the diffraction-limited focusing due to annular propagation of the plasmon with its nanofocusing by a tapered metal wedge (i.e. a metal film with reducing local thickness). The numerical finite-element analysis demonstrates strongly subwavelength resolution of the described structure with the achievable size of the focal spot of ~20 nm with up to ~150 times enhancement of the local electric field intensity. Detailed physical interpretations of the obtained results are presented and possible application as a new type of SNOM probe for subwavelength imaging, spectroscopy and sensing are also discussed.

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。