이정훈 교수

SmFeO3, a family of centrosymmetric rare-earth orthoferrites, is known to be nonferroelectric. However, we have found that SmFeO3 is surprisingly ferroelectric at room temperature with a small polarization along the b axis of Pbnm. First-principles calculations indicate that the canted antiferromagnetic ordering with two nonequivalent spin pairs is responsible for this extraordinary polarization and that the reverse Dzyaloshinskii-Moriya interaction dominates over the exchange-striction mechanis

Hybrid perovskites are currently the fastest growing photovoltaic technology, having reached a solar cell efficiency of over 20%. One possible strategy to further improve the efficiency of perovskite solar cells is to tune the degree of octahedral tilting of the halide frame, since this in turn affects the optical band gap and carrier effective masses. It is commonly accepted that the ion sizes are the main control parameter influencing the degree of tilting in perovskites. Here we re-examine th

First principles calculations on the hybrid perovskite CH3NH3PbI3 predict strong hydrogen-bonding which influences the structure and dynamics of the methylammonium cation and reveal its interaction with the tilting of the PbI6 octahedra. The calculated atomic coordinates are in excellent agreement with neutron diffraction results.

The lanthanum (La) modification is known to improve dielectric and magnetic properties of ${\text{BiFeO}}_{3}$ (BFO), a promising room-temperature multiferroic oxide. The effects of La doping on the variations of the off-centering distortion and the orbital mixing of BFO are experimentally studied, in conjunction with first-principles density-functional theory (DFT) calculations. Both the Fe-O bond anisotropy in the ${\text{FeO}}_{6}$-octahedron cage and the off-centering ferroelectric polarizat

Orexin-A and orexin-B (also called hypocretin-1 and hypocretin-2, respectively) are novel hypothalamic neuropeptides encoded by a single mRNA transcript; they stimulate food intake. We have determined the three-dimensional solution structure of human hypocretin-2/orexin-B using two-dimensional 1H-NMR data and dynamical simulated annealing calculations. On the basis of NOEs, 3JHNalpha coupling constants and hydrogen-deuterium exchange rates together with chemical shift indices, human hypocretin-2

Ammonia is a promising energy vector that can store the high energy density of hydrogen. For this reason, numerous adsorbents have been investigated as ammonia storage materials, but ammonia adsorbents with a high gravimetric/volumetric ammonia capacity that can be simultaneously regenerated in an energy-efficient manner remain underdeveloped, which hampers their practical implementation. Herein, we report Ni_acryl_TMA (TMA = thiomallic acid), an acidic group-functionalized metal-organic framewo

The family of diamine-appended metal-organic frameworks exemplified by compounds of the type mmen-M₂(dobpdc) (mmen = <i>N</i>,<i>N</i>'-dimethylethylenediamine; M = Mg, Mn, Fe, Co, Zn; dobpdc^4- = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) are adsorbents with significant potential for carbon capture, due to their high working capacities and strong selectivity for CO₂ that stem from a cooperative adsorption mechanism. Herein, we use first-principles density functiona

The combined effects of steric and hydrogen-bonding interactions enhance the elastic properties of MA-based hybrid perovskites relative to their inorganic counterparts. However, MA-induced octahedral tilting increases the effective carrier masses which results in a reduction in carrier mobility.

In eukaryotes, misfolded proteins must be distinguished from correctly folded proteins during folding and transport processes by quality control systems. Yeast peptide:N-glycanase (yPNGase) specifically deglycosylates the denatured form of N-linked glycoproteins in the cytoplasm and assists proteasome-mediated glycoprotein degradation by forming a complex with 26S proteasome through DNA repair protein, yRad23. Here, we describe the crystal structures of a yPNGase and XPC-binding domain of yRad23

A pseudo-binary solid solution formed with two structurally dissimilar end members possesses a structural phase boundary, commonly called the morphotropic phase boundary (MPB). Many of the technologically useful piezoelectric oxides exhibit their maximum piezoelectric responses at a characteristic composition that corresponds to the MPB. Here we present a first-principles approach that can predict the existence of the MPB and its unique chemical composition. By evaluating the composition-depende

Hybrid halide perovskites are promising for applications because of their favorable optoelectronic properties and low cost. Here we investigate the effects of hydrostatic pressure on the structural and electronic properties of (MA)PbI3 (MA = CH3NH3+) using first-principles density functional theory calculations. Our calculations predict that at a pressure of 0.23 GPa, the orthorhombic Fmmm phase becomes unstable with respect to a cubic Im3̅ phase, in good agreement with room-temperature experime

The controllability of carrier density and major carrier type of transition metal dichalcogenides(TMDCs) is critical for electronic and optoelectronic device applications. To utilize doping in TMDC devices, it is important to understand the role of dopants in charge transport properties of TMDCs. Here, the effects of molecular doping on the charge transport properties of tungsten diselenide (WSe₂ ) are investigated using three p-type molecular dopants, 2,3,5,6-tetrafluoro-7,7,8,8-tetr

A Reply to the Comment by R. D. Johnson, N. Terada, and P. G. Radaelli.Received 9 November 2011DOI:https://doi.org/10.1103/PhysRevLett.108.219702© 2012 American Physical Society