목차
1. 서론 1
2. 밀도범함수론의 기초 2
(a) Hohenberg-Kohn 정리와 Kohn-Sham 방정식 2
(b) 교환-상관 에너지, Exc 3
(c) Vext 계산을 위한 의사-포텐셜 방법 5
(d) USPP (극히 부드러운 의사-포텐셜)의 간략한 소개 7
(e) 모멘텀 공간에서의 Kohn-Sham 방정식과 에너지 8
(f) PAW (projector augmented-wave) 방법의 간략한 소개 9
3. 강유전/다강체 연구에의 응용 10
(a) 이웃원자간의 오비탈 혼성화와 강유전성의 발현 10
(b) 오비탈 자체 혼성화에 의해 유발되는 특이 강유전성 및 압전성 11
(c) 다강체에서 스핀-스핀 상호작용에 의해 유발되는 특이 강유전성 12
(d) 기타 강유전/다강체 연구에의 응용 15
참고문헌 16
Fig. 1. Schematic illustration of the replacement of the allelectron (AE) wavefunction [Ψz/r or more commonly ΨAE(r)] and core potential (broken lines) by a pseudo-wavefunction [ψps(r)] or more commonly [φps(r)] and pseudo-potential (solid lines). 5
Fig. 2. A schematic representation of the 1st Brillouin zone and the irreducible Brillouin zone (IBZ) in a 2D showing 4x4 mesh of k-points. 8
Fig. 3. (a) Schematic diagrams of the two distinct possibilities of Yb-OA orbital interactions, 5dz₂(Yb)-2pz(OA) and 6s(Yb)-2pz(OA) (b) A comparison of the orbitalresolved partial density of states for 5dz₂(Yb), 6s(YB).... 10
Fig. 4. Electronic band structures of the ZnO. (a) Band structure of the nonpolar P63/mmc phase along the surface k vectors of the high symmetry line of the first Brillouin zone as shown in the inset. (b) Band structure of the polar P63mc phase. 11
Fig. 5. Schematic orbital-interaction diagrams illustrating a sequential bonding mechanism responsible for the c-axis-oriented piezoelectricity.... 12
Fig. 6. A pictorial representation of the spin configuration for the four distinct multiferroic states of o-TbMn₂O5. The variation in the spin configuration associated with the electric-field-induced polarization switching is shown in the upper panel.... 13
Fig. 7. (a) Proposed structure of the Mn spins under a bias magnetic(H)-field along the a-axis. This modulated spin structure projected on (002) is characterized by the tilting-angle (φ) which is a measure of the deviation from the E-type spin... 14
Fig. 8. Sequential changes in the spin configuration with the variation of temperature. The spontaneous magnetization reversal observed at 5 K (TMR) is attributed to a long-range ordering of the Sm³+-spin moment which is opposite to the canted Fe³+-spin moment... 14
Fig. 9. Implementation of a high-density four-states multiferroic memory using the vertically aligned Mndoped BaTiO₃ nanorods array. (a-d) Schematic drawing of four distinct ferroic memory states implemented using... 16