• Journal of the Korean Chemical Society
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• v.55 no.6
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• pp.905-911
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• 2011

The possible minimum structures of $C_{60}(CH_2)_nOH$ (n=0~2) and $C_{60}(OH)_2$have been optimized using density functional theory (DFT) with the 6-311G (d,f) basis set. The harmonic vibrational frequencies and IR intensities are also determined to confirm that all the optimized geometries are true minima. Also zero-point vibrational energies (ZPVE) have been considered to predict the binding energies. The predicted binding energy of $C_{60}CH_2OH$ is about 10 kcal/mol more stable than the binding energy of $C_{60}OH$.

• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.2077-2082
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• 2009

The conformational and electronic properties of 2-cyano-3-(thiophen-2-yl)acrylic acid (TCA) in analogues used as sensitizers in dye-sensitized solar cells was examined using density functional theory (DFT) and natural bond orbital analysis methods. A relaxed potential energy surface scan was performed on NKX-2677 by rotating the C-C bond between the thiophene and cyanoacrylic acid which yielded activation energy barriers of about 13 kcal/mol for both E and Z configurations. The most stable conformation of all the analogues was E-180 except for NKX-2587 which has an electrostatic repulsion between the oxygen of the coumarin and the nitrogen of the cyanoacrylic acid. The increase in the electron delocalization between the thiophene and cyanoacrylic acid influences the stability for most of the analogues. But for NKX-2600, even though there was a greater deviation from the planarity of TCA, the stability was mainly due to the presence of a weak hydrogen bond between the hydrogen of the methyl group of the amine located in the donor moiety and the nitrogen of the cyanoacrylic acid. The vertical excitation energies of the analogues containing TCA were calculated by time-dependent DFT method. There were slight differences in its vertical excitation energies but the oscillator strengths vary significantly especially in the case of NKX-2600.

• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.2013-2018
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• 2014

The adsorption and decomposition of trimethylene oxide ($C_3H_6O$) molecule on the Al(111) surface were investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employed a supercell ($6{\times}6{\times}3$) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between $C_3H_6O$ molecule and Al atoms induce the C-O bond breaking of the ring $C_3H_6O$ molecule. Subsequently, the dissociated radical fragments of $C_3H_6O$ molecule oxidize the Al surface. The largest adsorption energy is about -260.0 kJ/mol in V3, V4 and P2, resulting a ring break at the C-O bond. We also investigated the decomposition mechanism of $C_3H_6O$ molecules on the Al(111) surface. The activation energies ($E_a$) for the dissociations V3, V4 and P2 are 133.3, 166.8 and 174.0 kJ/mol, respectively. The hcp site is the most reactive position for $C_3H_6O$ decomposing.

• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.2093-2096
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• 2014

2H-azirine, a less known acetonitrile isomer, is observed in matrix IR spectra from the precursor exposed to radiation from laser ablation of transition-metals. Its vibrational characteristics confirm the previous results, and those for the deuterated and $^{13}C$ substituted isotopomers are also newly reported. The weak absorptions are traced to the low production yield due to its high energy and low extinction constants. IRC computations reveal smooth inter-conversion between 2H-azirine and $CH_2NCH$, providing a rationale for the observed variation of their relative contents during photolysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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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.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.371-383
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• 2014

이 연구에서는 팔라듐 착물 $Pd(PPh_3)_2$을 사용한 bromotoluene과 morpholine간의 coupling reaction (Buchwald-Hartwig amination) 반응 메커니즘을 계산화학적 방법을 이용하여 연구하였다. 용매화 자유에너지를 고려한 중간체 에너지를 비교하였으며, 반응물질이 o-bromotoluene 일 때와 p-bromotoluene 일 때, 반응 중간체로 monophosphine 착물이 형성되는 경우와 bisphosphine 착물이 형성되는 경우를 비교하였으며, 반응 중간체로 bisphosphine 착물이 형성되는 경우 cis 이성질체가 중간체인 경우와 trans 이성질체가 중간체인 경우를 비교하였다. 그 결과, 반응물로 p-bromotoluene을 사용할 때 o-bromotoluene을 사용할 때보다 중간체가 상대적으로 더 안정하여 더 좋은 수득률을 얻을 수 있을 것으로 예상되었다. 또한 $Pd(PPh_3)_n(o-tolyl)(N(CH_2CH_2)_2O)$ (n=1 또는 2) 중간체를 제외하고는 모든 경우에서 bisphosphine 중간체가 형성되는 반응경로가 더 안정한 것으로 밝혀졌다. 그리고 $Pd(PPh_3)_2ArBr$의 경우 trans 이성질체가 cis 이성질체보다 안정하지만 $Pd(PPh_3)_2Ar(N(CH_2CH_2)_2O)$의 경우 반대로 cis 이성질체가 trans 이성질체보다 안정한 것으로 나타났다.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.14-16
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• 1988

With the development of VLSI technology, research on special processors for high-speed processing is on the increase and studies are focused on designing VLSI-oriented processors for signal processing. This paper processes a one-dimensional systolic array for Discrete Hartley Transform implementation and also processes processing element which is well described for algorithm. The discrete Hartley Transform(DHT) is a real-valued transform closely related to the DFT of a real-valued sequence can be exploited to reduce both the storage and the computation requried to produce the transform of real-valued sequence to a real-valued spectrum while preserving some of the useful properties of the DFT is something preferred. Finally, the architecture of one-dimensional 8-point systolic array, the detailed diagram of PE, total time units concept on implementation this arrays, and modularity are described.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.546-550
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• 2014

Relative reactivity of various carbonyl and acid derivatives in MPV-type (Meerwein-Ponndorf-Verley) reduction with an DIBAL(F) model has been studied via DFT and MP2 methods. Free energies of initial adduct formation (-Gadd) of DIBAL(F) model and carbonyls are in the order of amide < ester < aldehyde < ketone < acid chloride; in the alan-amide adduct, the developed positive charge at carbonyl carbon is expected to be stabilized by amide resonance, but in the acid chloride adduct it is destabilized by inductive effect of chloride. However the TS barrier energies (${\Delta}G_{TS}$) for the MPV-type hydride reduction of the carbonyl adducts are in the order of aldehyde < ketone < acid chloride << ester < amide; presumably decreasing order of electrophilicity of carbonyl carbon at adducts, which is well correlated with experimental data. It is noted that the relative reactivity of carbonyl derivatives in MPV-type reduction with DIBAL(X) is not governed by the alan-adduct formation energies, but follows the order of electrophilicity of carbonyl carbon of transition states.

• Bulletin of the Korean Chemical Society
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• v.26 no.8
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• pp.1229-1234
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• 2005

The conformational, configurtational behavior and the structure of N-2-(1,4-Dioxane)-N'-(4-methylbenzenesulfonyl)-O-(4-methylphenoxy) isourea 1 has been studied using DFT method. Calculations predict the imidoyl amino group of the dioxane ring prefers axial conformation and that the tosyl and tolyl groups about the C=N bond retain E configuration. The anomeric effect controls the population of dioxane ring conformers, and anomers. Intramolecular hydrogen bonds contribute to the stability of E isomers. The computational analysis of 1 complements the X-ray findings.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.979-982
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• 2003

본 논문은 단상 또는 3상의 AC 전원의 전류나 전압 또는 전력을 계측하기 위해 Analog Signal들을 Digital Signal로 변환하여 특정 Algorithm의 연산을 수행하여 결과를 얻는 과정을 Microprocessor를 이용하여 처리하는 방법은 산업현장이나 연구개발에서 흔히 사용하는 방법이다. 본 논문에서는 Microprocessor를 이용하여 보편화된 3가지의 계측 Algorithm인 DFT, True RMS, Summation Algorithm을 사용하여 동일 System에 3상 AC의 전류 부하를 일정 범위에서 가변 하여 인가시키면서 계측 값을 사용하여 Algorithm의 계측 결과의 오차율과 연산에 소요되는 시간과 외부 잡음인 Surge, Impulse, 정전기, 방파, 고조파에 대한 System의 처리 효율을 연구 하였다.