• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.6
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• pp.556-561
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• 2022

Computational material science as an application of Density Functional Theory (DFT) to the discipline of material science has emerged and applied to the research and development of energy materials and electronic materials such as semiconductor. However, there are a few difficulties, such as generating input files for various types of materials in both the same calculating condition and appropriate parameters, which is essential in comparing results of DFT calculation in the right way. In this tutorial status report, we will introduce how to create crystal structures and to prepare input files automatically for the Vienna Ab initio Simulation Package (VASP) and Gaussian, the most popular DFT calculation programs. We anticipate this tutorial makes DFT calculation easier for the ones who are not experts on DFT programs.

• Journal of the Korean Chemical Society
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• v.53 no.3
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• pp.257-265
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• 2009

The structures and metal affinities of the binding configurations of $Cu^{+}$ and $Cu^{2+}$ to proline have been investigated using the hybrid three-parameter Density Functional Theory(DFT/B3LYP). We found that the metal-proline bonding and the energy ordering of several conformers were very different in $Cu^{+}$-proline and $Cu^{2+}$-proline. For $Cu^{+}$-proline, the ground state structure was found to have a bidentated coordination in which $Cu^{+}$ was coordinated to the carbonyl oxygen and imino group nitrogen of neutral proline. On the contrary, the ground state structure of $Cu^{2+}$-proline involves chelation between the two oxygens of the carboxylate group in a zwitterionic proline. The metal ion affinity of proline of the most stable $Cu^{+}$-proline complex was calculated as 76.0 kcal/mol at 6-311++G(d,p) level, whereas the $Cu^{2+}$ ion affinity of proline was calculated as 258.5 kcal/mol.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.230-230
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• 2006

Density functional theory (DFT) calculations using the B3LYP hybrid functional and the 6-311++G(d,p) basis set have been performed to predict the wavelength dispersion of optical absorbance and refractive indices for organic compounds and polymers in the range between the vacuum UV (${\sim}157\;nm$) and near-IR (${\sim}850\;nm$). The DFT calculations can reproduce the experimental dispersions of absorbance and refractive indices with high accuracy and low costs. The calculated dispersions demonstrate that the judicious introductions of $-F\;and\;-CF_{3}$ into alicyclic and heterocyclic compounds are effective in reducing the absorption at shorter wavelengths. In addition, the calculated Abbe numbers that represent the refractive index dispersion in the visble region are linearly proportional to the calculated refractive indices at 589 nm.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3722-3726
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• 2013

Covalent functionalization of a $Zn_{12}O_{12}$ nano-cage with $CO_2$ molecule in terms of energetic, geometry, and electronic properties was investigated by density functional theory method. For chemisorption configurations, the adsorption energy of $CO_2$ on the $Zn_{12}O_{12}$ nano-cage for the first $CO_2$ was calculated -1.25 eV with a charge transfer of 1.00|e| from the nano-cage to the $CO_2$ molecule. The results show that $CO_2$ molecule was significantly detected by pristine $Zn_{12}O_{12}$ nano-cage, therefore the nano-cage can be used as $CO_2$ storage. Also, more efficient binding could not be achieved by increasing the $CO_2$ concentration. For Physisorption configurations, HOMO-LUMO gap of the configurations has not changed, while slight changes have been observed in the chemisorption configurations.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1481-1484
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• 2009

When isolated phenol or a small phenol-solvent cluster is excited to the $S_1\;state\;of\;{\pi}{\pi}^*$ character, the hydrogen atom of the hydroxyl group dissociates via a ${\pi}{\sigma}^*$ state that is repulsive along the O-H bond. We computationally investigated the substitution effects of an amino group on the excited state hydrogen transfer reaction of phenol. The time-dependent density functional theory (TDDFT) with B3LYP functional was employed to calculate the potential energy profiles of the ${\pi}{\pi}^*$ and the ${\pi}{\sigma}^*$ excited states along the O-H coordinate, together with the orbital shape at each point, as the position of the substituent was varied. It was found that the amino substitution has an effect of lowering the ${\pi}{\sigma}^*$ state and enhancing the excited state hydrogen transfer reaction.

• Bulletin of the Korean Chemical Society
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• v.24 no.11
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• pp.1649-1654
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• 2003

We have investigated substituent effect on the stabilization energies, and nucleus-independent chemical shifts of pentafulvalenes and on the electronic structures of the corresponding polypentafulvalenes to design environmentally stable semiconductive or conductive polymers. Geometrical optimizations of the molecules were carried out at the density functional level of theory with B3LYP hybrid functional and 6-311+G(d) basis set. Stabilization energies were estimated using isodesmic and homodesmotic reactions. As a criterion of aromaticity nucleus-independent chemical shifts of the molecules were computed using GIAO approach. For the polymers the geometrical parameters were optimized through AM1 band calculations and the electronic structures were obtained through modified extended Huckel band calculations. It is found that strong electronwithdrawing substituents increase isodesmic and homodesmotic stabilization energies of pentafulvalene, though it does not increase the aromaticity. Nitro-substituted pentafulvalene is estimated to have stabilization energy as much as azulene. However, substitution either with electron-donating groups or with electronwithdrawing groups does not significantly affect the electronic structures of polypentafulvalene and poly (vinylenedioxypentafulvalene).

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.127.1-127.1
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• 2013

Recent experimental evidence that fluorinated graphene creates local magnetic moments around F adatoms has not been supported by semilocal density-functional theory (DFT) calculations where the adsorption of an F adatom induces no magnetic moment in graphene. Here, we show that such an incorrect prediction of the nonmagnetic ground state is due to the self-interaction error inherent in semilocal exchange-correlation functionals. The present hybrid DFT calculation for an F adatom on graphene predicts not only a spin-polarized ground state with a spin moment of ${\sim}1{\mu}_B$, but also a long-range spin polarization caused by the bipartite nature of the graphene lattice as well as the induced spin polarization of the graphene states. The results provide support for the experimental observations of local magnetic moments in fluorinated graphene.

• Corrosion Science and Technology
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• v.21 no.1
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• pp.21-31
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• 2022

Potentiodynamic polarization, EIS measurements, quantum chemical calculations, and molecular dynamic simulations were used to investigate the corrosion behavior of mild steel in 0.5 M aqueous hydrochloric acid medium in the presence or absence of nystatin drug. Potentiodynamic tests suggested that this molecule could act as a mixed inhibitor due to its adsorption on the mild steel surface. The objective of this study was to exploit theoretical calculations to gain a better understanding mechanism of inhibition. Calculating the adsorption behavior of the investigated molecule on Fe (1 1 0) surface was accomplished using Monte Carlo simulation. Molecules were also investigated using Density Functional Theory (DFT), specifically PBE functional, in order to identify the link between molecular structure and corrosion inhibition behavior of the compound under investigation. Adsorption energies between nystatin and iron were estimated more accurately by utilizing Molecular Mechanics calculation with Periodic Boundary Conditions (PBC). Estimated theoretical parameters significantly assisted our understanding of the corrosion inhibition mechanism exhibited by this molecule. They were found to be in accord with experimental results.

• Prospectives of Industrial Chemistry
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• v.15 no.3
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• pp.39-48
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• 2012

현대 컴퓨터산업의 진보는 제일원리 전산법이 여러 연구개발 분야에 널리 사용되는 길을 열었다. 이 논문에서는 제일원리 전산법을 이용한 신 재생에너지의 고성능 나노 소재개발 및 디자인 연구사례를 통해 그 기초 원리와 다양한 응용분야 및 실험과의 효율적인 연계성 등을 소개하고자 한다.

• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.69-75
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• 2008

Tautomerism of pyrimidine base cytosine has been comparatively examined on nanoparticle and roughened plate surfaces of silver, gold, and copper by surface-enhanced Raman scattering (SERS). The SERS spectrum was found to be different depending on the metals and their substrate conditions suggesting the dissimilar population of various tautomers of cytosine on the surfaces. The ab initio calculations were performed at the levels of B3LYP, HF, and MP2 levels of theory with the LanL2DZ basis set to estimate the energetic stability of the tautomers with the metal complexes as well as the gas phase state. The amino group and N3-coordinated tautomer was predicted to be more favorable for bonding to Au, whereas the hydroxyl and N1-coordinated zwitter ionic form is most stable with Ag and Cu as a bidentate form from the DFT calculation. The binding energy with the Ag atom is calculated to be smaller than those with the Au and Cu atoms in line with the temperature-dependent SERS spectra of cytosine.