• Bulletin of the Korean Chemical Society
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• 제31권8호
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• pp.2219-2222
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• 2010

A density functional theory (DFT) study of $CO_2$ adsorption on barium oxide (BaO) adsorbents is conducted to understand the chemical activity of the oxygen site on the BaO (100) surface. This study evaluated the adsorption energies and geometries of a single $CO_2$ molecule and a pair of $CO_2$ molecules on the BaO (100) surface. A quantum calculation was performed to obtain information on the molecular structures and molecular reaction mechanisms; the results of the calculation indicated that $CO_2$ was adsorbed on BaO to form a stable surface carbonate with strong chemisorption. To study the interactive $CO_2$ adsorption on the BaO (100) surface, a pair of $CO_2$ molecules was bound to neighboring and distant oxygen sites. The interactive $CO_2$ adsorption on the BaO surface was found to slightly weaken the adsorption energy, owing to the interaction between $CO_2$ molecules.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.211.1-211.1
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• 2014

Recently, the scaling of conventional planar NAND flash devices is facing its limits by decreasing numbers of electron stored in the floating gate and increasing difficulties in patterning. Three-dimensional vertical NAND devices have been proposed to overcome these issues. Atomic layer deposition (ALD) is the most promising method to deposit charge trap layer of vertical NAND devices, SiN, with excellent quality due to not only its self-limiting growth characteristics but also low process temperature. ALD of silicon nitride were studied using NH3 and silicon chloride precursors, such as SiCl4[1], SiH2Cl2[2], Si2Cl6[3], and Si3Cl8. However, the reaction mechanism of ALD silicon nitride process was rarely reported. In the present study, we used density functional theory (DFT) method to calculate the reaction of silicon chloride precursors with a silicon nitride surface. DFT is a quantum mechanical modeling method to investigate the electronic structure of many-body systems, in particular atoms, molecules, and the condensed phases. The bond dissociation energy of each precursor was calculated and compared with each other. The different reactivities of silicon chlorides precursors were discussed using the calculated results.

• 한국전기전자재료학회논문지
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• 제35권6호
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• pp.556-561
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• 2022

밀도범함수이론(density functional theory, DFT)이 등장한 이래로, 이를 재료과학에 적용하여 에너지 재료 및 반도체와 같은 전자재료들의 연구개발에 활발하게 활용되고 있다. 하지만 DFT 계산 프로그램을 실행할 때 필요한 입력 파일 생성 시 여러 가지 소재들에 대해 동일한 계산 조건을 맞춰 주고 파라미터들을 알맞게 설정해 줘야 올바른 계산 결과 비교가 가능한데, 이런 부분들에 대해 진입 장벽이 높다는 어려움이 있다. 이에 본 논문에서는 Python Materials Genomics (pymatgen) 파이썬 패키지를 이용해 분자 및 결정구조를 다루고 널리 사용되는 DFT 계산 프로그램인 Vienna Ab initio Simulation Package (VASP) 및 Gaussian 입력 파일 생성에 대해 소개하고자 한다. 이를 통해 해당 프로그램에 대한 전문적인 지식이 많지 않더라도 보다 일관적인 계산 조건에서 결과들을 손쉽게 수행할 수 있게 되기를 기대한다.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.253-256
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• 2014

Functionalization of zigzag graphene nanoribbon (ZGNR) segment containing 120 C atoms with pyridine (3NV-ZGNR) defects was investigated on the basis of density-functional theory (DFT) calculations, results show that edge-modified ZGNRs by Sc can adsorb multiple hydrogen molecules in a quasi-molecular fashion, thereby can be a potential candidate for hydrogen storage. The stability of Sc functionalization is dictated by a strong binding energy, suggesting a reduction of clustering of metal atoms over the metal-decorated ZGNR.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.775-782
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• 2014

The importance of including spin-orbit interactions for the correct description of structures and vibrational frequencies of haloiodomethanes is demonstrated by density functional theory calculations with spin-orbit relativistic effective core potentials (SO-DFT). The vibrational frequencies and the molecular geometries obtained by SO-DFT calculations do not match with the experimental results as well as for other cations without significant relativistic effects. In this sense, the present data can be considered as a guideline in the development of the relativistic quantum chemical methods. The influence of spin-orbit effects on the bending frequency of the cation could well be recognized by comparing the experimental and calculated results for $CH_2BrI$ and $CH_2ClI$ cations. Spin-orbit effects on the geometries and vibrational frequencies of $CH_2XI$ (X=F, Cl, Br, and I) neutral are negligible except that C-I bond lengths of haloiodomethane neutral is slightly increased by the inclusion of spin-orbit effects. The $^2A^{\prime}$ and $^2A^{{\prime}{\prime}}$ states were found in the cations of haloiodomethanes and mix due to the spin-orbit interactions and generate two $^2E_{1/2}$ fine-structure states. The geometries of $CH_2XI^+$ (X=F and Cl) from SO-DFT calculations are roughly in the middle of two cation geometries from DFT calculations since two cation states of $CH_2XI$ (X=F and Cl) from DFT calculations are energetically close enough to mix two cation states. The geometries of $CH_2XI^+$ (X=Br and I) from SO-DFT calculations are close to that of the most stable cation from DFT calculations since two cation states of $CH_2XI$(X=Br and I) from DFT calculations are energetically well separated near the fine-structure state minimum.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.91-92
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• 2021

In the present work, we simulated and explained the bonding of three alkanethiols - hexanethiol (HT), decanethiol (DT), and 11-mercaptoundecanoic acid (MDA) - with Fe(110) surface and Fe2 clusters using Density Functional Theory (DFT) to probe the corrosion inhibition mechanisms. The interaction energies computed from periodic DFT calculations successfully predicted the experimental inhibition performance. We have found strong covalent bond formation between S(thiol) and Fe-atoms in both approaches, further confirmed by the projected density of states and electron density difference. Besides, natural bond orbital (NBO) charge distribution showed that DT had stronger electron-donation and back-donation synergic interactions with Fe-atoms.

• Bulletin of the Korean Chemical Society
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• 제35권12호
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• pp.3567-3570
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• 2014

The most stable adsorption structures and energies of four tautomers of 3-methyl-5-pyrazolone (keto-1, enol-1, keto-2, and enol-2) on Ge(100) surfaces were investigated using density functional theory (DFT) calculations. The enol-1, keto-2, and enol-2 tautomers, but not the keto-1 tautomer, were found to exhibit stable adsorption structures on the Ge(100)-$2{\times}1$ surface. Of these three adsorption structures, that of enol-2 is the most stable.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.189.2-189.2
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• 2014

The most stable adsorption structures and energies of four tautomerized forms (keto-1, enol-1, keto-2, and enol-2) of 3-methyl 5-pyrazolone (MP) adsorbed on Ge(100) surfaces have been investigated by Density Functional Theory (DFT) calculation method. Among its four tautomerized forms, we confirmed three tautomerized forms except keto-1 form show the stable adsorption structures when they adsorbed on the Ge(100)-$2{\times}1$ surface as we calculate the respective stable adsorption structures, activation barrier, transition state energy, and reaction pathways. Moreover, among three possible adsorption structures, we acquired that enol-2 form has most stable adsorption structure with O-H dissociated N-H dissociation bonding structure.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.215-215
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• 2011

The bonding configuration and adsorption stability of alanine and leucine adsorbed on Ge(100)-2${\times}$1 surface were investigated and compared using core-level photoemission spectroscopy (CLPES) and density functional theory (DFT) calculations. The bonding configuration, stability, and adsorption energies were evaluated for two different coverage levels. In both cases, the C 1s, N 1s, and O 1s core-level spectra at a low coverage (0.30 ML) indicated that the carboxyl and amine groups participated in bonding with the Ge(100) surface in an "O-H dissociated-N dative bonded structure". At high coverage levels (0.60 ML), both this structure and an "O-H dissociation bonded structure" were present. As a result, we found that alanine adsorbs more easily (lower adsorption energy) than leucine on Ge(100) surfaces due to less steric hindrance of side chain.

• Bulletin of the Korean Chemical Society
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• 제34권8호
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• pp.2491-2494
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• 2013

The effect of additives in an electrolyte solution on the conversion efficiency of a dye sensitized solar cell was investigated. A density functional theory (DFT) method was used to examine the physical and chemical properties of nitrogen-containing additives adsorbed on a $TiO_2$ surface. Our results show that additives which cause lower partial charges, higher Fermi level shifts, and greater adsorption energies tend to improve the performance of DSSCs. Steric effects that prevent energy losses due to electron recombination were also found to have a positive effect on the conversion efficiency. In this work, 3-amino-5-methylthio-1H-1,2,4-triazole (AMT) has been suggested as a better additive than the most popular additive, TBP, and verified with experiments.