• 제목/요약/키워드: $DV-X{\alpha}$ method

검색결과 29건 처리시간 0.021초

DV-Xα 분자 궤도법을 이용한 고강도 타이타늄 합금 설계 (A Study on the Design of High-Stength Titanium Alloys Using DV-Xα Molecular Orbital Method)

  • 백민숙;윤동주;원대희;김병일
    • 대한금속재료학회지
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    • 제49권9호
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    • pp.739-745
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    • 2011
  • Beta-type alloys are the most versatile class of titanium alloys. They offer the highest strength to weight ratios and very attractive combinations of strength, toughness, and fatigue resistance inlarge cross sections [1]. The present study was made to obtain useful information for the design of ${\beta}$-type titanium alloys with high-strength properties by using the $DV-X{\alpha}$ method. Employing two calculated parameters, the bond order (Bo) and the d-orbital energy level (Md) of alloying elements in ${\beta}$-type titanium alloy was introduced and used for prediction of mechanical properties. Thus, high-strength titanium alloys were designed by calculating the Md and Bo values of the previous and present titanium alloys.

제1원리 분자궤도계산법에 의한 $MnO_2$ 산화물 반도체의 전자상태에 미치는 불순물 첨가 효과의 계산 (Calculation on Effect of Impurity Addition on Electronic State of $MnO_2$ Oxide Semiconductor by First Principle Moleculat Orbital Method)

  • 이동윤;김봉서;송재성;김현식
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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    • pp.99-102
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    • 2003
  • The electronic structure of ${\beta}-MnO_2$ having impurities in the site of Mn was theoretically investigated by $DV-X_{\alpha}$ (the discrete variation $X{\alpha}$) method, which is a sort of the first principle molecular orbital method using Hatre-Fock-Slater approximation. The used cluster model was $[Mn_{14}MO_{56}]^{-52}$ (M = transient metals). Madelung potential and spin polarization were considered for more exact calculations. As results of calculations, the energy levels of all electron included in the model were obtained. The energy band gap and positions of impurity levies were discussed in association with impurity 34 orbital that seriously affect electrical properties of $MnO_2$. It was shown that the energy band gap decreased with the increase of the atomic number of transient metal impurity.

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DV-Xα 클러스터 계산법에 의한 Fe4N의 전자상태계산 (Electronic States Calculation of Fe4N by DV-Xα cluster calculation)

  • 송동원;이인섭;배동수
    • 한국재료학회지
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    • 제12권1호
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    • pp.44-47
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    • 2002
  • DV(Discrete Variation)-X${\alpha}$ cluster calculation was employed to calculate the electronic states of ${\gamma}'- Fe_4N$ which was one of iron nitride phases synthesized from plasma ion nitriding to improve surface hardness and wear resistance. The result of calculated electron density of states for Fe was similar to the result of band calculation. The cluster used for calculation of electronic states of ${\gamma}'-Fe_4N$ was based on $Fe_{14}N$ cluster which comprises 15 atoms. Finally the electronic states of ${\gamma}'- Fe_4N$ such as net-charge, band order, energy level, electron wave-function, and contour map for electron density were derived by the calculation.

분자궤도계산법에 의한 $\beta$-$MnO_2$의 전자상태 및 화학결합 계산 (Calculation on Electronic State and Chemical Bonding of $\beta$-$MnO_2$ by DV-X$\alpha$ Method)

  • 이동윤;김봉서;송재성;김현식
    • 한국결정학회지
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    • 제14권1호
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    • pp.16-23
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    • 2003
  • β-MnO₂ 전자상태와 화학결합을 하트리-폭-슬레이터 근사를 사용하는 제 1원리 분자 궤도법의 일종인 DV-X/sub α/ 법에 의해 이론적으로 조사하였다. 벌크상의 β-MnO₂에 대한 상태를 해석하기에 적합한 클러스터 모델을 결정하기 위하여, 여러 가지 다른 크기를 지닌 수종의 클러스터 모델들에 대한 계산을 행하였다. 실험적으로 측정된 XPS와 이론적으로 계산된 XPS를 비교함으로써, Mn/sub 15/O/sub 56/ 모델이 β-MnO₂의 전자 상태와 화학 결합을 계산하기에 가장 적합한 모델임을 결정하였다. 이 모델을 사용하여 에너지 준위, 상태 밀도, 유효 공유 결합 전하, 유효 전하, 전자 밀도 분포를 구하고, 이에 대한 고찰을 행하였다.

III, IV족 불순물이 첨가된 ZnO의 전자상태계산 (Calculation on Electronic Structure of ZnO with Impurities Belonging to III and IV Family)

  • 이동윤;김현주;구보근;이원재;송재성
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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    • pp.309-312
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    • 2004
  • The electronic structure of ZnO oxide semiconductor having high optical transparency and good electric conductivity was theoretically investigated by $DV-X_{\alpha}$(the discrete variation $X_{\alpha}$) method, which is a sort of the first principle molecular orbital method using Hatre-Fock-Slater approximation. The electrical and optical properties of ZnO are seriously affected by the addition of impurities. The imnurities are added to ZnO in order to increase the electric conductivity of an electrode without losing optical transparency. In this study, the effect of impurities of III and IV family on the band structure, impurity levels and the density of state of ZnO were investigated. The cluster model used for calculations was $[MZn_{50}O_{53}]^{-2}$(M=elements belonging to III and IV family).

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Y이 도핑된 ZnO의 전자상태 계산 (Calculation on Electronic State of Y-doped ZnO)

  • 이동윤;이원재;송재성;구보근;김현주
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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    • pp.172-173
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    • 2005
  • The electronic state of ZnO doped with Y was calculated using the density functional theory. In this study, the program used for the calculation on theoretical structures of ZnO and doped ZnO was Vienna Ab-initio Simulation Package (VASP), which is a sort of pseudo potential method. The detail of electronic structure was obtained by the descrite variational $X\alpha$ (DV-$X\alpha$) method, which is a sort of molecular orbital full potential method. The optimized crystal structures obtained by calculations were compared to the measured structure. The density of state and energy levels of dopant elements was shown and discussed in association with optical properties.

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Li의 첨가에 따른 Vanadium의 유화물과 산화물의 전자상태계산에 관한 연구 (A Study on the Electronic Structures of Li Intercalated Vanadium Sulfide and Oxide)

  • 정현철;김희진;원대희;윤동주;김양수;김병일
    • 대한금속재료학회지
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    • 제46권9호
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    • pp.604-608
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    • 2008
  • The layered compounds vanadium disulfide($VS_2$) and vanadium dioxide($VO_2$) intercalated with Li are investigated for using the Discrete Variational $(DV)-X{\alpha}$ molecular orbital method. The chemical bonding properties of the atoms were examined by bond overlap population of electronic states. The plot of density of states supports the covalent bonding properties by showing the overlap between the atoms. There is a strong tendency of covalent bonding between V-S and V-O. The intensity of covalent bonding of $VS_2$ is stronger than $VO_2$. The net charge of $LiVO_2$ is higher than that of $LiVS_2$. This results of the calculation of $VO_2$ and $VS_2$ indicate that $(DV)-X{\alpha}$ method can be widely applied in the new practical materials.

Application of DV-X$\alpha$ Method to ${\gamma}$-2CaO.SiO$_2$

  • Yamaguchi, Norio;Fujimori, Hirotaka;Ioku, Koji;Goto, Seishi;Nakayasu, Tetsuo
    • The Korean Journal of Ceramics
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    • 제6권4호
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    • pp.339-342
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    • 2000
  • In the present study, we attempted to apply DV-X$\alpha$ method to expressing the reactivity of materials. The expression of reactivity was discussed by comparison between ${\gamma}$-C$_2$G having hydraulic activity and ${\gamma}$-C$_2$S not having hydraulic activity at normal conditions. It was found that the model cluster used for calculation can finely reproduce the bulk and surface states using with and without point charge, respectively. The hydration state was also represented by placing OH ̄ on the surface of the cluster. It was calculated that the bond strength of the first layer (as surface) was bigger than that of inner layers (as bulk) for ${\gamma}$-C$_2$S while that of the first layer for ${\gamma}$-C$_2$G was smaller than that of inner layers. Subsequently a model in which OH ̄ is coordinated on Ca at the surface was also calculated. The bond strength with OH ̄ was stronger than that without OH ̄, while for ${\gamma}$-C$_2$G the bond strength with OH ̄ was weaker than that without OH ̄. From these results, it is concluded that the hydraulic activity depends on whether the bond strength for hydrated state becomes weaker than that unhydrated state or not.

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TiO2 전극 표면의 전자상태 계산 (Calculation on Surface Electronic State of $TiO_2$ Electrode)

  • 이동윤;이원재;송재성
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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    • pp.259-262
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    • 2003
  • The surface electronic state of rutile $TiO_2$, which is an oxide semiconductor and has a wide band gap of 3.1 $\sim$ 3.5 eV, was calculated by DV-$X_{\alpha}$ method, which is a sort of the first principle molecular orbital method and uses Hartre-Fock-Slater approximation. The $[Ti_{15}O_{56}]^{-52}$ cluster model was used for the calculation of bulk state and the $[OTi_{11}O_{34}]^{-24}$ model for the surface state calculation. After calculations, the energy level diagrams and the deformation electron density distribution map were compared in both models. As results, it was identified that the surface energy levels are found between the valence and conduction band of bulk $TiO_2$ on the surface area. The energy values of these surface-induced levels are lower than conduction band of bulk $TiO_2$ by 0.1 $\sim$ 1 eV. From this fact, it is expected that the surface energy levels act as donar levels in n-type semiconductor.

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Anodic deposition된 $MnO_2$ 막의 열분석 특성 (Thermal analysis of anodically deposited manganese oxide film)

  • 김봉서;이동윤;이희웅;정원섭
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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    • pp.900-903
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    • 2003
  • Using $DV-X{\alpha}$ method, it is calculated that nickel reduces the energy band gap of manganese oxide in 3 additives of titanium, nickel and tin. Therefore, it is estimated that the electrical conductivity of manganese-nickel oxide has the lowest value in 3 kinds of manganese oxide. The manganese oxide and manganese-nickel oxide which were produced by anodic deposition under $30mA/cm^2$ at room temperature in manganese sulfate and manganese-nickel sulfate solution were thermal-analyzed by DTA and TGA. The weight change of manganese oxide continuously decreased below $508^{\circ}C$ and kept constant at $518{\sim}600^{\circ}C$. However, the manganeses-nickel oxide transformed at the temperature range of $510{\sim}537^{\circ}C$. It is observed that the nickel addition to manganese oxide increases transformation temperature and its range.

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