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.

Neutral and Anionic Gold Decamers: Planar Structure with Unusual Spatial Charge-Spin Separation

Abstract: We have investigated the issue of two-dimensional (2D) versus three-dimensional (3D) structures for neutral-state Au10 and clarified the lowest-energy structure among a few 2D Au10(-) isomers. Though almost all previous works were based on density functional theory (DFT), we here carried out not only extensive DFT calculations but also high levels of ab initio calculations of Moller-Plesset second order perturbation theory (MP2), and coupled cluster theory with single and double excitations (CCSD) including perturbative triple excitations [CCSD(T)]. While DFT favors 2D structures, MP2 and CCSD(T) favor 3D structures for moderate-sized basis sets. However, we note that the basis-set superposition error (BSSE) corrections make the ab intio results favor 2D structures too. The near-degeneracy (driven by relativistic effects) of 5d and 6s orbitals of gold helps stabilize acute apex gold atoms, resulting in 2D structures. The planar triangular structures of a local minimum Au10 (triplet) and the global minimum Au10(-) show remarkable spatial charge-spin separation due to their singly occupied molecular orbital(s). By the same reason, Au10(-) shows much larger vertical detachment energy than other even-numbered gold cluster anions.

Ab initio studies of the conformations of methylamine and ethylenediamine: interaction forces affecting the structural stability

Abstract: The structures and conformational energies of methylamine and ethylenediamine have been studied extensively with ab initio molecular orbital theory. For methylamine, there are good linear relationships among the C-N bond length, cosine of the H-C-N-H dihedral angle, and conformational energy. For ethylenediamine which has numerous multiminima, we studied the stereoelectronic effect, steric effect, intramolecular hydrogen bonding, repulsion between hydrogens, and repulsion between lone-pair electrons. The major factor determining the conformational stabilities of the multiminima is found to be the stereoelectronic effect. The partial hydrogen bonding, though weak, contributes to the structural stability so that two isoenergetic gauche conformers become the lowest energy structures

Pt-like hydrogen evolution on a V2O5/Ni(OH)2 electrocatalyst

Abstract: We report a highly efficient and cost-effective binder-free catalyst for the hydrogen evolution reaction (HER) using V2O5 particles on nickel foam (NF) (V2O5/Ni(OH)2@NF). This low-cost catalyst exhibits Pt-like activity with a low overpotential of 39 mV at 10 mA cm−2 (lowest among V-based materials which are known to be generally non-explosive and safe) and long-term stability in a 1 M KOH solution. The overall performance is highly comparable to that of a commercial 20% Pt/C catalyst on NF. Furthermore, the V2O5/Ni(OH)2@NF outperforms the Pt/C catalyst at a higher current density (100 mA cm−2) which is more preferable for industrial applications. First principles calculations show that the remarkable HER activity is ascribed to the near-zero adsorption free energy (ΔGH*) on the Ni-site of Ni(OH)2@NF and the Ni- and O-sites of in situ generated V2O5@NF, due to the charge transfer arising from adsorbed O atoms on Ni(111), along with high conductivity of NF. O-adsorption on the Ni transition metal surface downshifts the d-band center of the transition metal, which helps in quick hydrogen desorption by weakening the hydrogen binding strength. As a result, most Ni fcc sites of V2O5/Ni(OH)2@NF are more active than pristine Ni fcc sites. The V2O5/Ni(OH)2@NF catalyst initiates overall water splitting at 1.53 V in a 6 M KOH solution for solar-to-hydrogen generation in a two-electrode set-up using a solar panel.

Theoretical Study of the Conformations and Strain Energies of [n,n]Metaparacyclophanes: Indication of Stable Edge-to-Face and Displaced Face-to-Face Conformers for n = 4.

Abstract: We have studied [n,n]metaparacyclophanes-model compounds exhibiting edge-to-face and displaced stacked aromatic-aromatic interactions-using semiempirical calculations for n = 2-5 and ab initio calculations for n = 2-4. For n = 2 and 3, the strain energies govern the conformational preference, while for n = 4 and 5 the aromatic-aromatic and strain energies are equally important. The 3,12-dithio[4,4]metaparacyclophanes exhibit edge-to-face aromatic-aromatic intereactions, while the [4,4]metaparacyclophanes and 2,11-dithio[4,4]metaparacyclophanes exhibit displaced stacked aromatic-aromatic interactions.

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。