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한 개의 CI가 치환된 YBCO에 대한 결합과 전자구조
이기학,박성수,이왕로,이한명 圓光大學校 1996 論文集 Vol.31 No.2
본 연구에서는 확장된 Huckel 분자궤도 tight binding 계산 방법을 사용하여 초전도체인 YBa₂Cu₃O 의 산소 원자 위치에 염소 원자가 각각 한 개씩 치환된 YBCO 계의 하전된 덩어리 모델의 전자구조와 성질을 연구하였다. 분자들의 isomorphism 문제를 분석함과 같이 염소 원자로 산소 원자 위치인 O1, O2p, O3p, O4p, O2n, O3n 과 O4n에 산소 원자 한개를 치환하였으며 또한 부가될수 있는 위치인 O5 에 부가하여 모든 가능한 조합에 대하여 계산을 하였다. 그 결과로 염소 원자로 O1 위치 또는 O5 위치에 대치된 YBa₂Cu₃O xClx 의 전자구조, band 구조 그리고 상태밀도 (DOS) 가 YBa₂Cu₃O 과 가장 비슷함을 보였다. 이것은 CuO₂층의 산소 원자가 초전도성에 매우 민감한 것을 암시한다. Using the extended Huckel molecular orbital tight binding (EHMO-TB) calculation, we have studied the electronic structure and properties of charged clusters model corresponding to one Cl-substituted YBCO in which O-atom(s) in regular site is replaced by Cl-atom(s) for superconducting YBa₂Cu₃O. In analogy to the isomorphism problem with molecules, we calculated all possible cases of one Cl-substitutions in O-sites with O1, O2p, O3p, O4p, O2n, O3n and O4n and case of one Cl-addition in vacancy with O5. Our results suggest that the electronic structure, the band structure, and density of states (DOS) of YBa₂Cu₃O xClx, with O1- or O5- site replaced by Cl appears to be the closest to that of YBa₂Cu₃O. This implies that the superconducting is very sensitive to the oxygen atoms of CuO₂layers.
Intergration of the Two-Center Radial Intergral Involving the Modified Bessel Functions
이기학 圓光大學校 1983 論文集 Vol.17 No.2
두 점 A와 B에 위치한 Slater 원자 궤도 함수의 two-center radial integrals 을 modified Bessel 함수를 사용하여 기준점 A를 중심으로 전개하여 공통좌표상에 기술하였고, 이 기준점에 대한 지름부 적분의 기본식을 유도하였다. 이 Slater원자 궤도 함수 전개식을 사용하여 얻은 two-center radial integral의 기본식과 Mulliken의 중첩 적분에 대한 radial part integrals를 비교 고찰하였다.
Trans MX_4Y_2형태착물에 대한 리간드의 알짜 유효 전하의 계산
박의서,이기학 全北大學校 基礎科學硏究所 1979 基礎科學 Vol.2 No.1
A method for calculation of the effective charge of ligands on trans MX_4Y_2 type complexes has been developed in this work. The gross atomic population of ligands is adopted for calculation of the effective charge of ligand instead of point charge. The calculated effective charge of ligands falls in the reasonable range.
4-nitro-N-(triphenyl phosphoranylidene)의 전기화학적 환원에 관한 연구
최창진,김일광,이기학,전병영,김봉원 圓光大學校 基礎自然科學硏究所 1984 基礎科學硏究誌 Vol.3 No.2
The electrochemical reduction of 4-nitro-N-(triphenyl-phosphoranylidene) in nonaqueous media has been examined by polarography, cyclic voltammetry and controlled-potential coulometry. The reduction of 4-nitro-N-(triphenylphosphoranylidene) proceeds by a one electron-transfer to form anion radical which undergoes both protonation and a second one electron reduction followed by cleavage of a phosphorous-phenyl bond was also observed after reduction of triphenylphosphine oxide which is one of the major products of the chemical reaction which follow the primary electrode process.
Lee, Chang-Hoon,Park, Sung-Soo,Lee, Wang-Ro,Lee, Kee-Hag Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.2
The geometrical structures and energetics of positively doubly charged fullerene dimer $(C_{60})_2{^{2+}}$ conformers were studied using semiempirical PM3 and MNDO, Hartree-Fock (HF), and Hybrid B3LYP density functional methods. The shape of the HOMO-LUMO for the three conformers was also analyzed. The gauche conformer was the most stable of the three conformers. The anti conformer was more stable than the syn conformer.
Lee, Seol,Lee, Ji Young,Lee, Kee Hag Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.8
The hybrid density-functional (B3LYP/6-31G(d,p)) method was used to analyze the substitution effect on the $C_{20}H_{20}$ cage based on calculation of the frontier orbitals of fifteen $C_{20}H_{17}(OH)_3$ derivatives. All substitution products were geometrically optimized without constraints and confirmed by frequency analysis. The results suggest that the cis-1 cis-1 cis-2 regioisomer is the most stable isomer, which implies that hydrogen bonding exerts a stronger effect on the relative energies of the trihydroxide than long-range interactions. Thus, this supports the experimental result in which the bisvicinal tetrol was of particular preparative-synthetic interest. While the LUMO of each of the $C_{20}H_{17}(OH)_3$ regioisomers was equivalently delocalized over the void within the cage, the HOMO was limitedly delocalized on substituents and carbons in close proximity to the substituents. The characteristics of the HOMO of each of the regioisomers vary based on the substitution sites. This indicates that the 15 regioisomers of each $C_{20}H_{20}$ trisubstituted derivative might undergo an entirely different set of characteristic chemical reactions with electrophilic reagents. The results further suggest that the penta-substituted OH groups on the surface of the fullerene cage are more likely to be localized on a pentagon than to be homogeneously delocalized.
Lee, Kee-Hag,Lee, Wang-Ro,Choi, U-Sung Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.7
Using the extended Hackel molecular orbital method in connection with the tight binding model, we have studied electronic structure and related properties of the charged cluster models relating to superconducting $YBa_{2}Cu_{3}O_{7-x}$, crystals in which O-atoms in regular sites were selectively replaced with Se atoms. In analogy to the isomorphism problem with molecules, we discuss all possible combinations of Se-substitutions in O-sites with one, two, and four Se atoms. The calculations are carried out within charged cluster models for analogues of YBa-copper oxide. Our results suggest that the electronic structure of the symmetrically Se-substituted or Se-added compound is closer to that of the YBCO superconducting compound than that obtained from the unsymmetrical substitution. This applies in particular if O is replaced with Se around the Cu(1) site. Symmetrical substitutions in the $CuO_2$ layers give rise to large variations in the electronic structure of $YBa_{2}Cu_{3}O_{7}$. This is consistent with the fact that superconductivity is very sensitive to the electronic population of the $CuO_2$ layers.
Single Organic Molecules Designed as Nanoscale Connectors: Fullerene Isoxazoline Derivatives
Lee, Han-Myong,Lee, Chang-Hoon,Cho, Min-Sil,Hwang, Yong-Gyoo,Lee, Kee-Hag Korean Chemical Society 2004 Bulletin of the Korean Chemical Society Vol.25 No.12
Recently a fullerene isoxazoline was reported as an example for nanoscale connectors in molecular electronic devices. The construction of nanoscale devices is a potentially important area of technology. By using the semiempirical PM3 calculation, we optimized the structures for two fullerene isoxazoline derivatives and thirteen regioisomers of the second addition of a nitride oxide to a fullerene isoxazoline derivative. Our results suggest that fullerene isoxazoline derivatives could be used as nanoscale connectors with the possibility of attaching of spacer units in a specific angle arrangement.
Lee, Ji-Hyun,Lee, Chang-Hoon,Park, Sung-S.,Lee, Kee-Hag Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.1
We studied the relative stability and atomic structure of five $C_{20}^{2+}$ isomers obtained by two-electron ionization of a $C_{20}$ cage (the smallest fullerene). All the isomers are bond-stretch isomers, i.e., they differ in bond length. In particular, in one of the isomers with Ih symmetry, all the bond lengths are equal. Full geometry optimizations of the dipositive ion $C_{20}^{2+}$ were performed using the hybrid density functional (B3LYP/6-31G(d)) methods. All isomers were found to be true minima by frequency analysis at the level of B3LYP/6-31G(d) under the reinforced tight convergence criterion and a pruned (99,590) grid. The zero-point correction energy for the cage bond-stretch isomers was in the increasing order $D_{2h}<C_{2h}<C_2<T_h<I_h$ of $C_{20}^{2+}$. The energy difference among the isomers of cage dipositive ions was less than that among neutral cage isomers. Our results suggest that these isomers show bond-stretch isomerism and that they have an identical spin state and an identical potential energy curve. Although the predominant electronic configurations of the isomers are similar, the frontier orbital characteristics are different, implying that we could anticipate an entirely different set of characteristic chemical reactions for each type of HOMO and LUMO.