• 한국전기전자재료학회논문지
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• 제35권6호
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• pp.556-561
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• 2022

밀도범함수이론(density functional theory, DFT)이 등장한 이래로, 이를 재료과학에 적용하여 에너지 재료 및 반도체와 같은 전자재료들의 연구개발에 활발하게 활용되고 있다. 하지만 DFT 계산 프로그램을 실행할 때 필요한 입력 파일 생성 시 여러 가지 소재들에 대해 동일한 계산 조건을 맞춰 주고 파라미터들을 알맞게 설정해 줘야 올바른 계산 결과 비교가 가능한데, 이런 부분들에 대해 진입 장벽이 높다는 어려움이 있다. 이에 본 논문에서는 Python Materials Genomics (pymatgen) 파이썬 패키지를 이용해 분자 및 결정구조를 다루고 널리 사용되는 DFT 계산 프로그램인 Vienna Ab initio Simulation Package (VASP) 및 Gaussian 입력 파일 생성에 대해 소개하고자 한다. 이를 통해 해당 프로그램에 대한 전문적인 지식이 많지 않더라도 보다 일관적인 계산 조건에서 결과들을 손쉽게 수행할 수 있게 되기를 기대한다.

• 대한화학회지
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• 제49권1호
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• pp.7-15
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• 2005

• 대한화학회지
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• 제48권5호
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• pp.537-541
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• 2004

• EDISON SW 활용 경진대회 논문집
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• 제6회(2017년)
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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.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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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).

• 대한화학회지
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• 제65권1호
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• pp.9-14
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• 2021

이 연구에서는 1기압 298 K 기체 상태에서 페난트렌에 두 개의 OH 라디칼이 연쇄적으로 작용하여 페난트렌이 분해되는 반응 과정을 B3LYP/6-31G(d,p) 기저함수를 사용하여 DFT 계산을 수행하였다. 계산 결과 두 개의 OH 라디칼이 연쇄적으로 페난트렌에 작용하는 경우에도 phenanthren-9-ol 생성 반응이 phenanthren-1-ol 생성 반응보다 유리할 것으로 예측된다. 한편 OH 첨가와 H 추출 과정에 대한 우선성은 상온에서 OH 첨가 과정이 유리할 것으로 예측되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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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.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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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.

• 전기학회논문지P
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• 제55권1호
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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.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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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.