Decoupling Lattice and Magnetic Instabilities in Frustrated CuMnO.

The AMnO delafossites (A = Na, Cu) are model frustrated antiferromagnets, with triangular layers of Mn spins. At low temperatures ( = 65 K), a 2/ → 1̅ transition is found in CuMnO, which breaks frustration and establishes magnetic order. In contrast to this clean transition, A = Na only shows short-range distortions at .

Spin-chain correlations in the frustrated triangular lattice material CuMnO.

The Ising triangular lattice remains the classic test-case for frustrated magnetism. Here we report neutron scattering measurements of short range magnetic order in CuMnO, which consists of a distorted lattice of Mnspins with single-ion anisotropy. Physical property measurements on CuMnOare consistent with 1D correlations caused by anisotropic orbital occupation.

Is artificial intelligence magic dust for big-science facilities?

AI is no magic dust: for it to become a true discovery accelerator, much work is needed to make it transparent and robust.

Response to comment on 'Hydrogen bonds in crystalline d-alanine: diffraction and spectroscopic evidence for differences between enantiomers'.

A response is given to comments by Bürgi & Macchi [ (2018), , 654-657] about Belo [ (2018), , 6-12.].

Hydrogen bonds in crystalline d-alanine: diffraction and spectroscopic evidence for differences between enantiomers.

Enantiomeric amino acids have specific physiological functions in complex biological systems. Systematic studies focusing on the solid-state properties of d-amino acids are, however, still limited. To shed light on this field, structural and spectroscopic studies of d-alanine using neutron powder diffraction, polarized Raman scattering and calculations of harmonic vibrational frequencies were carried out.

Big-Science facilities in Europe need greater coordination of resources.

The leading role in science played by crystallography is heavily dependent on Big-Science facilities. The need for Europe-wide coordination of operational resources in Big Science is discussed with particular reference to neutron sources.

Charge order at the frontier between the molecular and solid states in Ba3NaRu2O9.

We show that the valence electrons of Ba3NaRu2O9, which has a quasimolecular structure, completely crystallize below 210 K. Using an extended Hubbard model, we show that the charge ordering instability results from long-range Coulomb interactions. However, orbital ordering, metal-metal bonding, and formation of a partial spin gap enforce the magnitude of the charge separation.

Solitonic lattice and Yukawa forces in the rare-earth orthoferrite TbFeO3.

The random fluctuations of spins give rise to many interesting physical phenomena, such as the 'order-from-disorder' arising in frustrated magnets and unconventional Cooper pairing in magnetic superconductors. Here we show that the exchange of spin waves between extended topological defects, such as domain walls, can result in novel magnetic states. We report the discovery of an unusual incommensurate phase in the orthoferrite TbFeO(3) using neutron diffraction under an applied magnetic field.

Polymorphism and piezochromicity in the three-dimensional network-based phosphate RbCuPO4.

Rubidium copper phosphate, RbCuPO(4), forms two room-temperature polymorphs that have been investigated with neutron powder diffraction. Polymorph (II) can be converted quantitatively into (I) by grinding the material or by pelletization, and the phase transition is accompanied by a significant colour change from very pale green to sky blue. Polymorph (II) can be obtained essentially free of (I) by quenching from 723 K.

Raman and neutron scattering study of partially deuterated L-alanine: evidence of a solid-solid phase transition.

Raman and neutron experiments using specific isotope labeling were combined in order to study the dynamics and structure of L-alanine. Inelastic neutron and Raman scattering data of C(2)H(4)(ND(2))CO(2)D are discussed in relation to the doubling of the lattice parameter a observed by means of neutron powder diffraction in C(2)D(4) (NH(2))CO(2)H. The major changes accompanying the phase transition are found in the vibrational frequencies involving the torsional vibration tau(CO(2)(-)), which is clearly affected by the hydrogen bonds between the protons of the ammonium group and the oxygen atoms of the carboxylate group.

Similarities between structural distortions under pressure and chemical doping in superconducting BaFe2As2.

The discovery of a new family of high-T(C) materials, the iron arsenides (FeAs), has led to a resurgence of interest in superconductivity. Several important traits of these materials are now apparent: for example, layers of iron tetrahedrally coordinated by arsenic are crucial structural ingredients. It is also now well established that the parent non-superconducting phases are itinerant magnets, and that superconductivity can be induced by either chemical substitution or application of pressure, in sharp contrast to the cuprate family of materials.

Metal-insulator transition and orbital order in PbRuO3.

Anomalous low temperature electronic and structural behavior has been discovered in PbRuO3. The structure [space group Pnma, a=5.563 14(1), b=7.

Dynamics of Water in NaxCoO2.yH2O.

Incoherent inelastic neutron scattering experiments were performed on Na0.7CoO2 and Na0.28CoO2.

Hydrogen in N-methylacetamide: positions and dynamics of the hydrogen atoms using neutron scattering.

This work reports neutron diffraction and incoherent neutron scattering experiments on N-methylacetamide (NMA), which can be considered the model building block for the peptide linkage of polypeptides and proteins. Using the neutron data, we have been able to associate the onset of a striking negative thermal expansion (NTE) along the a-axis with a dynamical transition around 230 K, consistent with our calorimetric experiments. Observation of the NTE raises the question of possible proton transfer in NMA, which, from our data alone, still cannot be settled.

Structural isotopic effects in the smallest chiral amino acid: observation of a structural phase transition in fully deuterated alanine.

A first study of possible changes instigated by deuteration in amino acids was carried out using neutron diffraction, inelastic neutron scattering, and Raman scattering in l-alanine, C2H4(NH2)COOH. Careful analysis of the structural parameters shows that deuteration of l-alanine engenders significant geometric changes as a function of temperature, which can be directly related to the observation of new lattice vibration modes in the Raman spectra. The combination of the experimental data suggests that C2D4(ND2)COOD undergoes a structural phase transition (or a structural rearrangement) at about 170 K.