We report our recent structural study on the polymer in room-temperature ionic liquid (IL) solutions by using neutron/X-ray scattering. Small-angle neutron scattering (SANS) measurement was made on poly(benzyl methaceyrate) (PBnMA) in fully deuterated 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C₂mIm] [TFSA]) solution and the LCST phase behavior was characterized from the structural viewpoint. The SANS was also carried out for poly(N-isopropyl acrylamide) (PNIPAm) in IL which shows UCST phase separation. It was found from the results that the phase behavior strongly depends on the solvation of polymers at the local scale. Therefore, we tried to perform high-energy X-ray diffraction for the polymer solutions, which allow us to discuss the microscopic solvation structure. We finally discussed the relationship between nano- and micro-scale structures in the polymer/IL systems.

This article reports the recent discovery of NaCl-type lanthanum monohydride using synchrotron radiation x-ray diffraction and neutron diffraction measurements under high pressure. We have found that fcc-LaH₂ decomposes into two phases，which have different hydrogen compositions，the H-poor and H-rich phases，at 11 GPa at room temperature by synchrotron radiation x-ray diffraction. This decomposition is interpreted in terms of a disproportionation reaction. Recent neutron diffraction measurements on LaD₂ confirmed the formation of a NaCl-type LaD as the D-poor phase. This is the first observation of a formation of the rare-earth metal monodeuteride. Present result indicates that that rare-earth metal can form a series of stoichiometric hydrides，such as mono-，di-，and trihydride with the fcc metal lattice.

In recent years, interrelation between spin and lattice degrees of freedom in frustrated magnets have been attracting much attention. In such systems, complex magnetic structures stabilized by frustrated exchange interactions between spins break inversion symmetry and induce a ferroelectric polarization. In this study, we have performed dielectric measurements and neutron diffraction experiments on the delafossite AgFeO₂. The neutron diffraction experiment demonstrated successive magneto-structural phase transitions at T_N1 = 15 K and T_N2 = 9 K. The magnetic structure for 9 K ≤ T ≤ 15 K is a spin-density wave with a temperature dependent incommensurate modulation k = ( -1, q, 1/2 ; q ~ 0.384). Below 9 K, the magnetic structure turns into elliptical cycloid with the incommensurate propagation vector k = (-1/2, q, 1/2; q ~ 0.206). Based on the deduced magnetic point-group symmetry m1′ of the low temperature polar phase, we conclude that the ferroelectric polarization in AgFeO₂ is perpendicular to the monoclinic b axis and is driven by the inverse Dzyaloshinskii-Moriya effect with two orthogonal components, p^→₁ ∝ r^→_ij × (S^→_i × S^→_j ) and p^→₂ ∝ S^→_i × S^→_j.

The human amyloid disorders, familial amyloid polyneuropathy and senile systemic amyloidosis are caused by insoluble transthyretin (TTR). Dissociation of the TTR tetramer appears to be the rate-determining step in amyloid cascade and the formation of amyloid fibrils is known to be promoted by lowered pH. In order to reveal the molecular mechanisms of the pH sensitivity and structural stabilities of TTR, neutron diffraction studies were conducted using IBARAKI Biological Crystal Diffractometer at J-PARC. The neutron structure solved at 2.0 Å revealed the protonation states of His88 and the detailed hydrogen-bond network depending on the protonation states of His88. This hydrogen-bond network is involved in monomer-monomer and dimer-dimer interactions, suggesting that the double protonation of His88 by acidification breaks the hydrogen-bond network and causes the destabilization of TTR.

This Article gives an introduction of crystal and magnetic structure refinements usinf angular dispersive neutron powder diffractometers. Some useful information for material researchers who want to try neutron powder diffraction experiments is provided.