In this article, I have reviewed a series of research on a various phase transitions such as (1) structural phase transitions of perovskite compounds driven by soft phonons, (2) pressure-induced molecular dissociation and metallization observed in solid halogens, and (3) the “Devil's Flower” type phase diagram observed in two compounds with frustrating interactions. Also commented is on the so-called “Small Science at Large Facility” typically symbolized by neutron and synchrotron radiation experiments like the present research.
In industry, protein crystallography is used in mainly two technologies. One is structure-based drug design, and the other is structure-based enzyme engineering. Some successful cases together with recent advances are presented in this article. The cases include the development of an anti-influenza drug, and the introduction of engineered acid phosphatase to the manufacturing process of nucleotides used as umami seasoning.
It is well known that B-site randomness contributes to the appearance of relaxor phenomena in the lead-based complex perovskite Pb(B'B")O3. But the microscopic mechanism of the effect of B-site randomness on the systems has not been understood yet. Among the Pb(B'B")O3 systems, Pb(In1/2Nb1/2)O3(PIN) has drawn much attention because it can be in the antiferroelectric (AFE), ferroelectric (FE), or relaxor state depending on B-site randomness. We review the recent progress in our understanding of the effect of B-site randomness on PIN from the experimental viewpoint. As a conclusion of the arguments, we also introduce the frustration mechanism in Pb(B'B")O3.
Atomic Pair Distribution Function (PDF) is a one of local structure analysis. PDF analysis is a powerful method for ferroelectrics in which domain structure exists. A deviation arises between average and local structures under the influence of the ferroelectric domain configuration. The local structure analysis of BaTiO3 and BiMg0.5Ti0.5O3 is shown as an example of application to the ferroelectric materials of PDF analysis.
Recently, a new spherical aberration corrected electron microscope called as R005 has been developed. Since very sharp electron probe of 30 mrad in convergent semi-angle is realized, the special resolution reaches to 47 pm in scanning transmission electron microscopy, which is the world best performance. In this review, we show that lithium ions are visualized in the spinel structure using R005. We found that the number of lithium atoms at the column was countable. In addition, we show that individual arsenic and antimony dopant atoms in the silicon crystal three-dimensionally.
Atg7 is a noncanonical E1 enzyme that activates Atg8 and transfers it to Atg3 (E2 enzyme), thus playing an essential role in conjugating Atg8 with phosphatidylethanolamine and thus in autophagy. Atg7 protomer is comprised of two globular domains, the N-terminal domain (NTD) and the C-terminal domain (CTD), and forms a homodimer through CTD. Atg7-Atg8 complex structures and biochemical analyses revealed that Atg8 is initially recognized by the C-terminal tail of CTD and is then transferred to the adenylation domain in CTD, where Atg8 Gly116 is adenylated and thioester-linked to the catalytic cysteine of Atg7. Atg8 is then transferred to Atg3 bound to the NTD of the opposite protomer within an Atg7 dimer via a trans mechanism.
A new class of superparamagnetism was found in relaxor ferroelectrics having magnetic ions 2/3BiFeO3-1/3BaTiO3. The polar nanoregion (PNR), which governs the relaxor ferroelectric property, affects the magnetic ordering significantly, and the resulting magnetic nano-domains are the new origin of superparamagnetism. The temperature variations in the sizes of the magnetic domains and PNRs estimated by our neutron diffraction measurements support this picture. The superparamagnetism induced by PNR is very unique because of its inherent connection between dielectric and magnetic properties.
Polarized neutron diffraction (PND) investigations were conducted for a single-crystal of a dinuclear octahedral high-spin cobalt(II) complex, using the local site susceptibility tensor method. The local induced magnetic moments were observed on cobalt(II) ions, revealing an angle of 37(1)°. Previously the compound was found to show a characteristic magnetic behavior, which was thought to be due to the significant magnetic anisotropy caused by an angle between the local axes of cobalt(II) ions. The angle obtained by PND was in good agreement with the result of magnetic analysis, and PND methods were shown to be very useful for studying highly-anisotropic molecular paramagnetic compounds.
We have investigated nanoscaled domain configuration of Pb(Ti1-xZrx)O3 (PTZ) and (1-x)Pb(Mg1/3Nb2/3)O3- xPbTiO3 ((1-x)PMN-xPT) in the monoclinic phase around a morphotropic phase boundary (MPB) region thoroughly by means of a transmission electron microscopy (TEM), in order to clarify mechanism of the enhancement of the piezoelectric effect. Two types of domain structures with inhomogeneous configuration were found around the MPB region. One is domain structures characterized by the formation of the nanoscaled herringbone-type domain structures with the ~10 nm width inside the macroscopic-sized banded domains with the 100~200 nm width. The other is as an aggregation of nanoscaled domains with the average size of about 10 nm. An in-situ TEM observation revealed that these nanoscaled domain structures are inherent to the monoclinic phase, which should be responsible for the excellent piezoelecrtric response.