• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.496-501
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• 2007

Recently, as MEMS and NEMS devices have been widely used in the various engineering applications, the characteristics of nanoscale systems are investigated in the limelight. However, as opposed to a macroscale system, the identification of the state of nanoscale systems is extremely hard because they can include only the order of $10^{3}\sim10^{5}$ molecules, which requires highly expensive and accurate experimental apparatus for an investigation. This limitations make the study on nanoscale system use computer simulations. Therefore, it is strongly required to identify the state of nanoscale system simulated in computer simulation. In these molecular dynamics(MD) study, we suggest that the potential energy of individual molecule can be used as criterion for defining the state of clusters or nanoscale systems. In addition, we compared the phase state from the potential energy with one from the radial distribution function(RDF) for verification. The comparison showed that the intermolecular potential energy can be used as a criteria distinguishing the phase state of nanoscale systems (This study will be published soon in the KSME transaction of the section B).

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.59-60
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• 2002

In this digest, we briefly review our current molecular dynamics (MD) simulations that utilize both the reactive empirical bond order potential (REBO) and the adaptive intermolecular REBO (AIREBO) potential energy functions. The AIREBO potential includes intermolecular interactions, so that self·assembled monolayers, and liquids, can be modeled. We have examined the mechanical and tribological properties of model self assembled monolayers and amorphous carbon films. Self-assembled monolayers are modeled by covalently bonding hydrocarbon chains to diamond substrates. Because the REBO potentials can model chemical reactions, specific compression and sliding induced chemical reactions were identified.

• 대한화학회지
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• 제40권1호
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• pp.20-27
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• 1996

분광학적 실험 자료들로부터 안정하고 정확한 위치에너지를 역으로 얻어내는 방법에 대하여 연구하였다. 이러한 역과정 방법은 비선형 역과정 문제에서 야기되는 불안정성을 위치에너지가 유연하게 연속적이라는 제한 조건을 사용하여 최적의 해를 얻어내는 Tikhonov의 규칙화에 기초를 두고 있다. 이 방법의 장점은 특정한 형태의 위치에너지 변수를 맞추는 보통의 방법과는 달리 위치에너지를 분자간 거리의 연속함수로 다루었다. 이 방법을 실험적으로 얻은 Ar-Ar계의 분광학적 자료에 적용하여 전 구간에서 정확한 위치에너지를 찾아가는 것을 보여주었고, Morse나 RKR 방법으로 얻은 위치에너지의 부정확한 먼거리 인력 부분을 보정할 수 있음을 보여주었다.

• Bulletin of the Korean Chemical Society
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• 제35권9호
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• pp.2738-2742
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• 2014

Geometry relaxation effects on the formation of benzene excimer were investigated by means of ab initio calculation at SOS-CIS($D_0$)/aug-cc-pVDZ level. In the case of T-shaped dimer configuration, intermolecular interactions in the excited states are found to be nearly the same as those in the ground state and structural deformations are limited within a single molecule; the geometry relaxation effects are then negligible and singlet-triplet energy gap remains constant. As for face-to-face eclipsed dimer, on the other hand, both molecules undergo structural change. As a result, intermolecular interactions in the excited states are significantly different than those in the ground state. Although the intermolecular distances obtained from potential energy curve calculation with frozen molecular structures are in qualitative agreement, the excited-state binding energies are notably overestimated with respect to those at optimized structures. In particular, the effects are calculated to be larger in $T_1$ state and hence singlet-triplet energy gap, which reduces markedly in this configuration, is underestimated without relaxation.

• Bulletin of the Korean Chemical Society
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• 제19권6호
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• pp.634-641
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• 1998

Quasiclassical trajectory calculations were carried out for the reactions of $H+H_2$ (V=O, J=O) and its isotope variants on the Siegbahn-Liu-Truhlar-Horowitz potential energy surface for the relative energies E between 6 and 150 kcal/mol. The goal of the work was to understand the inter- and intramolecular isotope effects. We examine the relative motion of reactants during the collision using the method of analysis that monitors the intermolecular properties (internuclear distances, geometry of reactants, and final product). As in other works, we find that the heavier the incoming atom is, the greater the reaction cross section is at the same collision energy. Using the method of analysis we prove that the intermolecular isotope effect is contributed mainly by differences in reorientation due to the different reduced masses. We show that above E=30 kcal/mol recrossing also contributes to the intermolecular isotope effect. For the intramolecular isotope effect in the reactions of H+HD and T+HD, we reach the same conclusions as in the systems of $O(^3P)+HD$, F+HD, and Cl+HD. That is, the intramolecular isotope effect below E=150 kcal/mol is contributed by reorientation, recrossing, and knockout type reactions.

• 대한기계학회논문집B
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• 제31권5호
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• pp.435-447
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• 2007

Recently, as MEMS and NEMS devices have been widely used in the various engineering applications, the characteristics of nanoscale systems are investigated in the limelight. However, as opposed to a macroscale system, the identification of the state of nanoscale systems is extremely hard because they can include only the order of $10^3{\sim}10^5$ molecules, which requires highly expensive and accurate experimental apparatus for an investigation. This limitations make the study on nanoscale system use computer simulations. Therefore, it is strongly required to identify the state of nanoscale system simulated in computer simulation. In this molecular dynamics(MD) study, we suggest that the potential energy of individual molecule can be used as criterion for defining the state of clusters or nanoscale systems. In addition, we compared the phase state from the potential energy with one from the radial distribution function(RDF) for verification. The comparison showed that the intermolecular potential energy can be used as a criteria distinguishing the phase state of nanoscale systems.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2678-2683
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• 2007

The interaction between metal molecules and liquid metal molecules was modeled in the molecular scale and simulated by the molecular dynamics method in order to understand behaviors of the cluster on metallic surface in collision process. Lennard-Jones potential had been used as intermolecular potential, and only attraction 때 d repulsion had been used for the behavior of the cluster on the metal surface. As results, the behavior of the cluster was so much influenced by the cluster of liquid metal temperature and function of molecules forces, such as attraction and repulsion, in the collision progress. These results of simulation will be the foundation for the micro fabrication manufacturing by using spray application technology.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2702-2707
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• 2007

The purpose of this study is to calculate the behavior of molecules for the generation of homogeneous thin-films in the process of spray deposition. The calculation system was composed of a suface molecular region and droplet molecular region. The thin-film was generated when droplet molecules fell to surface molecules. Lennard-Jones potential had been used as intermolecular potential, and only attraction 때 d repulsion had been used for the behavior of the droplet on the solid surface. As results, the behavior of the droplet was so much influenced by the surface temperature in the spray deposition process. High temperature of surface has higher porosity and larger spread area. It was found that simulation results generally agreed well with previous the experimental results. This simulation result will be the foundation for the deposition processes of industry.

• Bulletin of the Korean Chemical Society
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• 제6권4호
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• pp.183-186
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• 1985

The lattice vibrational calculation of orthorhombic hydrogen chloride is performed using physically realistic potential function which can reproduce the X-ray structure and heat of sublimation of the low temperature phase. The polar coordinates representation is introduced in order to describe the intermolecular interactions in a molecular crystal. The splitting in internal modes is calculated as 49 $cm^{-1}$ and the other modes are in good agreement with experimental results.

• 대한화학회지
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• 제21권6호
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• pp.395-403
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• 1977

액체이론(Significant Structure Theory)를 단원자 분자로부터 다원자 분자에 이르는 여러 액체혼합물에 적용하여 전 농도 범위에서 액체 혼합물의 활동도 계수를 계산했다. 단원자 분자계(Ar-Kr, Kr-Xe)와 이원자 분자계$(Ar-O_2,\;N_2-CO)$와 메탄-크립톤계의 액체혼합물의 활동도 계수는 ${\delta}E_s$ 수정 변수에 의해 좋은 결과를 얻었다. 아르곤-질소, 산소-질소, 그리고 메탄-프로판계에 대해서는 이 외에 ${\delta}$V, ${\delta}$n 수정 변수가 더 필요했다.