• Title, Summary, Keyword: DFT calculation

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Dissociation Curves of Transition Metal Compounds

  • Go, Dong-Hyeok;Song, Su-Hwan;Sim, Eun-Ji
    • Proceeding of EDISON Challenge
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    • pp.11-15
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    • 2017
  • We present a study of transition metal compounds using density functional theory (DFT), and density-corrected density functional theory(DC-DFT). By replacing the self-consistent density with that obtained from Hartree-Fock calculation, i.e., HF-DFT, the abnormality driven by self-interaction error is removed in several important cases. We discuss when and how HF-DFT works by examining 3d orbital dimers using approximate functionals and by comparing the results from self-consistent-DFT and HF-DFT with experimental values.

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Coverage Dependent Adsorption Configuration of Phenylalanine on Ge(100)

  • Yang, Se-Na;Yun, Yeong-Sang;Kim, Ye-Won;Hwang, Han-Na;Hwang, Chan-Guk;Kim, Gi-Jeong;Kim, Se-Hun;Lee, Han-Gil
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.78-78
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    • 2010
  • The Adsorption structures of phenylalanine on Ge(100) surface have been investigated as a function of coverage using high-resolution photoemission spectroscopy (HRPES) and density functional (DFT) calculation. To converge these experimental and theoretical conclusion, we systematically performed HRCLPES measurements and DFT calculation for various coverage in the adsorption structures of phenylalanine molecules on the Ge(100) surface. In this study, we found two different adsorption structure as a function of coverage in phenylalanine on Ge(100), monitoring three core level spectra (Ge 3d, C 1s, N 1s, and O 1s) using HRPES Through analysis of the binding energies, we confirmed that O-H dissociated and N dative-bonded structure emerges at low coverage (0.10 ML), which is the same to the result of glycine and alanine on Ge(100) system, whereas O-H dissociation structure also appears at higher coverage. Moreover, we observed the shape of phenyl group being included in phenylalanine is changed from flat to tilting structure at final state using DFT calculation. Through the spectral analysis for phenylalanine, we will demonstrate variation of coverage dependent structural change for phenylalanine on Ge(100) surface using experimental (HRPES) and theoretical studies (DFT calculation).

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A DFT Study for the Reaction Pathway(s) of Polycyclic Aromatic Hydrocarbons I: Phenanthrene Degradation with two OH Radicals (다고리 방향족 탄화수소의 반응 경로에 대한 DFT 연구 I: 2개의 OH 라디칼에 의한 페난트렌의 분해 반응)

  • Lee, Min-Joo;Lee, Byung-Dae
    • Journal of the Korean Chemical Society
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    • v.65 no.1
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    • pp.9-14
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    • 2021
  • In this study, the DFT calculation was performed using the B3LYP/6-31G(d,p) basis sets for the reaction process in which phenanthrene decomposes due to the chain reaction of two OH radicals on phenanthrene in the gaseous state of 298 K at 1 atm. As a result of the calculation, even when two OH radicals act on phenanthrene in a chain, the reaction for producing phenanthren-9-ol is predicted to be more advantageous than the reaction for producing phenanthren-1-ol. On the other hand, it was predicted that the OH addition process at room temperature would be advantageous for the priority of the OH addition and H abstraction process.

The Evidence of Tautomerization of 2-thiazoline-2-thiol on Ge (100) Surface

  • Park, Yeong-Chan;Yang, Se-Na;Kim, Ye-Won;Im, Hui-Seon;Kim, Se-Hun;Lee, Han-Gil
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.213-213
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    • 2012
  • We first confirm the tautomerization of 2-thiazoline-2-thiol on Ge (100) surface using CLPES and DFT calculation. We clearly confirmed that there exist two different molecular structures (we well show in our poster) in C 1s, N 1s, and S 2p CLPES spectra. Moreover, we obtained two plausible adsorption structures using DFT calculation which are that one is s-dative bonded structure and the other is SH dissociated-N-dative bonded structure although their stabilities are different on Ge (100) surface. We will investigate this interesting result for the confirmation of tautomerization of 2-thiazoline-2-thiol molecule adsorbed on Ge (100) surface.

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A Study of Mg Capping Inside p-tert-butylcalix[4]arene Adsorbed on a Ge(100) Surface

  • Shin, Minjeong;Lee, Myungjin;Lee, Hangil
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.135-135
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    • 2013
  • The electronic and adsorption structures of Mg and p-tert-butylcalix[4]arene (p-TBCA) adsorbed onto a Ge(100) surface under a variety of sample conditions were characterized using high-resolution photoemission spectroscopy (HRPES) and their corresponding DFT calculation results. Interestingly, after 0.10 ML p-TBCA molecules had been adsorbed onto a Ge(100) surface, subsequent adsorption of a small amount of metallic Mg (~0.10 ML) resulted in the formation of a capped structure inside the pre-adsorbed p-TBCA molecules. The adsorption structures resulting from further deposition of Mg (~0.50 ML) onto the Ge(100) surface were monitored based on the surface charge state and Mg 2s core level spectrum. Work function measurements clearly indicated the electronic structures of the Mg and p-TBCA adsorbed onto the Ge(100) surface. Moreover, we confirmed that three different adsorption structures are experimentally favorable at room temperature through DFT calculation results.

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The Design of UFR with Fast Frequency Measurement Technique (고속의 주파수 계측 알고리즘을 갖는 저주파 계전기 설계)

  • Park, Jong-Chan;Kim, Byung-Jin
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.55 no.1
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    • pp.1-5
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    • 2006
  • In this paper, the frequency estimator and DFT filter gain compensation for UFR(Under Frequency protection Relay) is introduced. Due to the sudden appearance of generator loads or faults in power system, the frequency is supposed to deviate from its nominal value. Because a frequency calculation is based on phase information, it needs sufficient sampling data to figure out a precious frequency. Therefore the frequency measurement for UFR needs excellent qualities such as high speed and precision with low sampling frequency Authors propose the frequency estimator which compares the vector differences and the DFT filter gain compensation which identifies DFT filter error and correct it. Using the frequency estimator and compensation, UFR which has the 0.01[ms] calculation delay and 0.003[Hz] measurement error is implemented with digital processor.

Inter-row Adsorption Configuration and Stability of Threonine Adsorbed on the Ge(100) Surfaces

  • Lee, Myungjin;Park, Youngchan;Jeong, Hyuk;Lee, Hangil
    • Bulletin of the Korean Chemical Society
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    • v.34 no.4
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    • pp.1055-1060
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    • 2013
  • The adsorption structures of threonine on the Ge(100) surface were investigated using core-level photoemission spectroscopy (CLPES) in conjunction with density functional theory (DFT) calculations. CLPES measurements were performed to identify the experimentally preferred adsorption structure. The preferred structure indicated the relative reactivities of the carboxyl and hydroxymethyl groups as electron donors to the Ge(100) surface during adsorption. The core-level C 1s, N 1s, and O 1s CLPES spectra indicated that the carboxyl oxygen competed more strongly with the hydroxymethyl oxygen during the adsorption reaction. Three among six possible adsorption structures were identified as energetically favorable using DFT calculation methods that considered the inter- and intra-bonding configurations upon adsorption onto the Ge(100) surface. These structures were O-H dissociated N dative inter bonding, O-H dissociated N dative intra bonding, O-H dissociation bonding. One of the adsorption structures: O-H dissociated N dative inter bonding was predicted to be stable in light of the transition state energies. We thus confirmed that the most favorable adsorption structure is the O-H dissociated N dative-inter bonding structure using CLPES and DFT calculation.