• 대한화학회지
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• 제40권4호
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• pp.264-272
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• 1996

ASED-MO(Atom Superposition and Electoron Delocalization-Molecular Orbtal)이론을 이용하여 Pt(lll)과 ${\upsilon}-Al_2O_3$(III) 표면 모델에 대한 계면간 결합 세기에 관해 연구하였다. $Al^{3+}$의 환원 정도가는 알루미나 뭉치(cluster)에 대한 산소와 알루미늄의 비에 따라 달라진다. $Al^{3+}$의 환원 정도가 크면 클수록 Pt 원소들에 대해 강한 결합 에너지를 가진다. 산소로 덮인 ${\gamma}-Al_{20}_3$(III) 표면과 Pt 계면간 결합이 매우 약하지만 백금의 산화 조건에서의 결합은 매우 강하다. 백금 표면에서 부분적으로 빈 O-2p 띠(band)와 $Al^{3+}$ dangling surface orbital로 전하가 이동하는 전하이동(charge transfer) 메카니즘에 의해 백금과 알루미나 계면간 결합은 가능하다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.61-62
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• 2002

In order to clarify the contact mechanism between specimen surface and probe tip in the surface observation by the AFM (atomic force microscope) or the FFM (friction force microscope), several molecular dynamics simulations have been performed. In the simulation, a 3-dimensional simulation model is proposed where the specimen and the probe are assumed to consist of mono-crystal line copper and a carbon atom respectively and the effect of cantilever stiffness is also taken into considered. The surface observation process on a well-defined Cu{100} is simulated. The influences of cantilever stiffness on the reactive force images and the behavior of probe tip were evaluated. As a resuIt, several phenomena similar to those observed by the actual surface observation experiment, such as double-slip behavior and dispersion in the stick-slip wave period were observed.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.61-61
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• 2011

Using ab initio calculations, we study the MgO(001) and Fe/MgO(001) surface phases and the effects of interface structure on the Fe/MgO magnetic anisotropy. The surface phase diagrams of MgO(001) and Fe/MgO(001) show that the most stable surface structures are either defect-free surface or the surfaces with oxygen vacancies in c($2{\times}1$) periodicity for the systems. By the formations of the oxygen vacancy rows on MgO(001) surface, the in-plane magnetic anisotropy energy of Fe overlayer is reduced while the perpendicular magnetic anisotropy energy is increased from 0.1 to 0.5 meV per Fe atom.

• 대한기계학회논문집
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• 제14권3호
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• pp.747-754
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• 1990

본 연구에서는 장시간 가공하는 경우 가공량과 가공물에 입사되는 이온 빔의 입사각도에 따라 이온 스파터 가공이 표면거칠기에 미치는 영향에 대해서 연구해 보았 다.

• Bulletin of the Korean Chemical Society
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• 제8권4호
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• pp.291-296
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• 1987

Vibrational spectroscopy has been applied to the benzenethiol molecule adsorbed on the silver surface. The results of infrared and Raman spectral studies have led to the conclusion that benzenethiol is chemisorbed dissociatively on the silver surface by rupture of S-H bond and the benzenethiolate formed upon adsorption is bound to silver via its sulfur atom. It seemed more likely that benzenethiol is adsorbed as being inclined to the silver surface. On contact with oxygen, the geometry of the adsorbed species appeared to bear a resemblance to that of silver benzenethiolate salt. The infrared bands of adsorbed species remained with little decrease of intensity even after the prolonged evacuation at 673 K, indicating that benzenethiol is very strongly chemisorbred to the silver surface.

• 한국전산구조공학회논문집
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• 제22권4호
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• pp.331-334
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• 2009

본 논문에서는 원자적 계산(atomistic calculation)을 위한 해석적 모델로 surface relaxation model을 제시한다. 기존의 분자정역학(molecular statics)이 모든 원자의 위치를 자유도로 선정하여 사용하는데 반하여, 이 모델은 면내방향에 해당하는 두 개의 자유도로 나노박막의 원자 위치를 기술하는 매우 간단한 방법이다. 본 연구에서는 surface relaxation model을 이용하여 표면응력(surface stress)과 표면강성계수(surface stiffness tensor)와 같은 표면인자(surface parameter)의 계산을 수행하고, surface stress model을 이용하여 평형상태에서의 원자의 위치정보를 계산한다. 그리고 surface relaxation model을 검증하기 위하여 분자동역학 전산모사(molecular dynamics simulation)의 수치 결과가 제시되며, 본 연구에서 계산한 equilibrium strain과 비교 검증한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.140.2-140.2
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• 2016

Despite the growing interest in GeTe as a archetypal displacive ferroelectric material as well as the basis of related materials used in data-storage applications, atom-resolved study of single crystalline GeTe surface been lacking. Using low temperature scanning tunneling microscopy (STM) and spectroscopy (STS), we investigated as-cleaved and annealed surfaces of GeTe. We found that as-cleaved GeTe(111) surface is composed of at least two kinds of terraces at 78 K. While two terraces show metallic characteristics, they also exhibit distinctive I-V spectra and imaging conditions, with each being attributed to Ge-terminated, and Te-terminated surfaces respectively. GeTe(111) surfaces annealed at moderately elevated temperature introduces intricate networks of extended defect structures. We will present these data and discuss the role of vacancies in the formation of these structures.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2369-2376
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• 2007

N2O has been found from experimental and theoretical considerations to bind on-top to the Pd(110) surface in a tilted end-on fashion via its terminal N atom. We use a frontier orbital description of the bonding interactions in the Pd-N2O system to obtain molecular insight into the catalytic mechanism of the activation of N2O by the Pd(110) surface giving rise to the formation of N2 and O on the surface. For the tilted end-on N2O binding mode, the LUMO 3π of N2O has good overlap with the Pd dσ and dπ orbitals which can serve as the electron donors. The donor-acceptor orbital overlap is favorable for electron transfer from Pd to N2O and is expected to dominate the surface reaction pathway of N2O decomposition.

• Bulletin of the Korean Chemical Society
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• 제15권11호
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• pp.933-939
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• 1994

Using an atom superposition and electron delocalization molecular orbital (ASED-MO) method, we have investigated the vibrational and chemisorptive properties of adsorbates on a Pt(100) surface during CO oxidation. The calculated vibrational stretching frequency for a predicted structure of $[CO{\cdot}{\cdot}{\cdot}O]^*$ complex is 1642 $cm^{-1}$. The CO bond stretches by 0.05 ${\AA}$ when adsorbed on one-fold site, and is tilted by 30 ${\AA}$ from the surface normal. We find the decrease in CO vibrational frequency on going from the one-fold to the high coordination sites. Binding at the two-fold site is predicted to be favored for $Pt_{18}(100)$ and at the 1-fold site for $Pt_{23}(100)$. From the calculations of the steric interactions, we have found that pre-adsorbed oxygen modifies the surface so that CO is adsorbed on the one-fold site ordered in a $(\sqrt{2}{\times}{\sqrt}{2})R45^{\circ}$. Our results are in good agreement with recent experimental findings of Hong et al. [J.Phys. Chem. 1993, 97, 1258].

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.985-994
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• 1997

The reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on Fe(110) surface is studied by use of classical trajectory procedures. Flow of energy between the reaction zone and bulk solid phase has been treated in the generalized Langevin equation approach. A London-Eyring-Polanyi-Sato energy surface is used for the reaction zone interaction. Most reactive events are found to occur in strong single-impact collisions on a subpicosecond scale via the Eley-Rideal mechanism. The extent of reaction is large and a major fraction of the available energy goes into the vibrational excitation of H2, exhibiting a vibrational population inversion. Dissipation of reaction energy to the heat bath can be adequately described using a seven-atom chain with the chain end bound to the rest of solid. The extent of reaction is not sensitive to the variation of surface temperature in the range of Ts=0-300 K in the fixed gas temperature, but it shows a minimum near 1000 K over the Tg=300-2500 K.