• 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.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.604-610
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• 2023

The nitrogen reduction reaction (NRR), which produces NH₃ by reducing N₂ under ambient conditions, is attracting attention as a promising technology that can reduce energy consumption in industrial processes. We investigated the adsorption behaviors at various active sites on the Ni (100) surface, which is widely used among catalytic metal surfaces capable of adsorbing and activating N₂, based on density-functional theory calculations. We also investigated two N₂ adsorption structures, so-called end-on and side-on structures. We find that for the end-on case, N₂ is adsorbed on a top site, and the reaction proceeded in a distal pathway, while for the side-on case, N₂ is adsorbed on a bridge site, and the reaction proceeded with enzymatic pathway. Finally, this study provides insight into the adsorption of metal catalyst surfaces for the NRR reactions based on the calculated Gibbs free energy profiles of the thermodynamically most favorable pathways.

• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.387-396
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• 2015

The DFT and ab initio calculations have been performed to elucidate hydrogen interaction of HOOO-(H₂O)_n (n=1~5) clusters. The optimized geometries, harmonic vibrational frequencies, and binding energies are predicted at various levels of theory. The trans conformer of HOOO monomer is predicted to be thermodynamically more stable than cis form at the CCSD(T) level of theory. For HOOO-(H₂O)_n clusters, the geometries are optimized at B3LYP/aug-cc-pVTZ and CAM-B3LYP/aug-cc-pVTZ levels of theory. The binding energy of HOOO-H₂O cluster is predicted to be 6.05 kcal/mol at the MP2//CAM-B3LYP/ aug-cc-pVTZ level of theory after zero-point vibrational energy (ZPVE) and basis set superposition error (BSSE) correction. The average binding energy per H₂O is increased according to adding a H₂O moiety in HOOO-(H₂O)_n clusters up to 7.2 kcal/mol for n=5.

• Journal of the Korean Chemical Society
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• v.59 no.2
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• pp.117-124
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• 2015

The DFT and ab initio calculations have been performed to elucidate hydrogen interaction of hydrogen polyoxide dimers, $H_2O_n-H_2O_m$ (n=1-4, m=1-4). The optimized geometries, harmonic vibrational frequencies, and binding energies are predicted at various levels of theory. The harmonic vibrational frequencies of the molecules considered in this study show all real numbers implying true minima. The higher-order correlation effect were discussed to compare MP2 result with CCSD(T) single point energy. The binding energies were corrected for the zero-point vibrational energy (ZPVE) and basis set superposition errors (BSSE). The largest binding energy predicted at the CCSD(T)/cc-pVTZ level of theory is 8.18 kcal/mol for $H_2O_4-H_2O_3$ and the binding energy of water dimer is predicted to be 3.00 kcal/mol.

• Geotechnical Engineering
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• v.12 no.3
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• pp.5-16
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• 1996

Based on many experimental results on fine silica sands, the strength relation between triaxial and plane strain tests is expressed as a function of both density and mean effective principal stress at failure. Stress ratio of mean normal stress to deviatoric stress at failure is a well defined function of shear angle of friction, This ratio decreases with increasing shear angle of friction. Intermediate principal stress is also expressed in terms of major and minor principal stresses and a relatively good agreement between theoretical and observed angles of failure plane in plane strain test is confirmed.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.521-526
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• 2007

Density functional calculations have been performed for the reactions of perfluoroalkylsilane and alkylsilane with silica surfaces. The (100) and (111) surfaces of ${\beta}-cristobalite$ are used as two possible models of the hydroxylated amorphous silica surface. This is the crystalline phase of silica with density and refractive index closest to those of amorphous silica. Moreover, two ${\beta}-cristobalite$ surfaces have the two types of silanol groups, namely the single silanols and the geminal silanols. We investigate the possible adsorption structure and formation energy of perfluoroalkylsilane and alkylsilane molecules with two type of silanol groups. The results will be compared with cluster and slab model.

• Journal of the Korean Chemical Society
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• v.25 no.5
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• pp.291-299
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• 1981

A test particle kinetic theory for reaction dynamics in liquids is presented at the repeated ring collision level for the hard sphere model. A kinetic equation for the equilibrium time correlation function of the reactive test particle phase space density is derived and the rate kernel expression for the reversible chemical reaction of the type A +B ${\rightleftharpoons$ C + D in the presence of inert solvent S is obtained by the projection operator method.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.154-160
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• 2008

We investigated molecular polarity by using theoretical means and comparing empirical solvent polarity. Our approach employed electrostatic potentials at the molecular surface calculated by density functional methods. A number of molecular descriptors related to molecular polarities were computed from molecular surface electrostatic potentials. Among computed molecular descriptors, the most positive electrostatic potential provided the best correlation with the empirical solvent polarities. A regression equation was developed in order to predict molecular polarities of molecules whose experimental solvent polarities were unknown. The new regression equations were utilized in estimating solvent polarities of cubane derivatives which are considered important precusors of high-energy density meterials.

• Journal of the Korean Chemical Society
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• v.52 no.6
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• pp.614-621
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• 2008

• Journal of the Korean Chemical Society
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• v.48 no.6
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• pp.568-576
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• 2004

Density functional theory calculations are presented for dicyanoacetylene $N{\equiv}C-C{\equiv}C-C{\equiv}N$ and its geometrical isomers. The structures and harmonic frequencies are computed by the BLYP theory employing the 6-311G^{\ast}$ basis set. A variety of isomers are predicted, and the relative energies are compared to estimate their thermodynamic stability.