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곽지민 ( Ji Min Kwak ),강창종 ( Chang-jong Kang ) 충남대학교 기초과학연구원 2022 충남과학연구지 Vol.39 No.1
In this study, we briefly review the basic concepts of band theory in solid-state systems. We take the two-dimensional graphene as a reference system and apply one-orbital tight binding model in order to compute the electronic structure of graphene. We compare the tight binding model with density functional theory calculations and find that the two methods are in good agreement.
이차원 단층 구조를 가지는 카고메 격자 물질 AV<sub>3</sub>Sb<sub>5</sub> (A = K, Rb, Cs)의 물리학적 성질
임준희 ( Jun Hee Im ),강창종 ( Chang-jong Kang ) 충남대학교 기초과학연구원 2022 충남과학연구지 Vol.39 No.1
Kagome lattice materials of AV<sub>3</sub>Sb<sub>5</sub> (A= K, Rb, Cs) have exotic physical properties such as charge density wave (CDW), superconductivity, and anomalous Hall effect. Since previous AV<sub>3</sub>Sb<sub>5</sub> studies have been mainly focused on the three-dimensional bulk system, in this study we investigate the low-dimensional AV<sub>3</sub>Sb<sub>5</sub> system within density functional theory (DFT). From the DFT calculations, we found that the two-dimensional monolayer Kagome lattice materials of AV<sub>3</sub>Sb<sub>5</sub> also show the similar CDW states as observed in the bulk system. Moreover, the CDW phases in the two-dimensional system have more stable than those in the three-dimensional system. It indicates that the lowering dimensionality makes the Kagome lattice materials more stable and it is able to tune the system into one with desired physical properties.
조민기 ( Minki Cho ),강창종 ( Chang-jong Kang ) 충남대학교 기초과학연구원 2022 충남과학연구지 Vol.39 No.1
Density functional theory (DFT) is an essential tool for computing the electronic structure of atoms, molecules, and solid-state materials. In this paper, we briefly review the current status of DFT including some basic explanation of many-body Hamiltonian, Born-Oppenheimer approximation, Hohenberg-Kohn theorem, and Kohn-Sham equation. The last two concepts, Hohenberg-Kohn theorem and Kohn-Sham equation, are the most important ones of DFT, hence we summarize the two ones intensively in this review.
전자구조의 양자역학적 계산을 위한 밀도범함수이론 개념 요약
최지원 ( Jiwon Choi ),강창종 ( Chang-jong Kang ) 충남대학교 기초과학연구원 2022 충남과학연구지 Vol.39 No.1
In this article, we briefly review density functional theory and its current status on computing the electronic structure in solid-state systems. In a weakly correlated system, density functional theory explains the electronic structure observed in angle-resolved photoemission spectroscopy measurements. Hence, density functional theory is a typical method to compute the electronic structure of a solid and we introduce the basic concept of the theory.
김재헌 ( Jae-heon Kim ),강창종 ( Chang-jong Kang ) 충남대학교 기초과학연구원 2023 충남과학연구지 Vol.40 No.1
In this study, we present a brief review of the fundamental concepts of band theory in solid-state systems. We take several systems, including Si, Al, and Cu (non-magnetic systems), as well as Ni (a magnetic system), as reference systems. We apply density functional theory (DFT) to compute their electronic structures and discuss how material properties could be inferred from the DFT calculations.
고온 초전도체 MgB<sub>2</sub> 물질의 전자구조 및 포논 분산 연구
곽지민 ( Jimin Kwak ),강창종 ( Chang-jong Kang ) 충남대학교 기초과학연구원 2023 충남과학연구지 Vol.40 No.1
In this study, we performed electron and phonon band calculations to determine the critial temperature of uperconductivity for MgB<sub>2</sub> using first-principle density functional theory calculations. The experimentally reported critical temperature of MgB2 is 39 K, while the computed critical temperature is 29 K. Based on these findings, we aim to design new materials with a high-Tc.