N. B. Bolotina

Atomic structure of boron suboxycarbide B(C,O)0.155

AbstractThe structure of a high-pressure boron suboxycarbide B(C,O)0.1555 single crystal has been studied for the first time. The unit-cell parameters are ah = 5.618(1), ch = 12.122(1) Å, V = 331.38(1) Å3, sp. gr. R

X-ray and neutron diffraction study of the defect crystal structure of the as-grown nonstoichiometric phase Y0.715Ca0.285F2.715

\bar 3

Relationship between the defect structure and fluorine-ion conductivity of La1 − ySryF3 − y (0 ⩽ y ⩽ 0.15) crystals according to X-ray and neutron diffraction data

m, Rhkl = 0.0479. The established common structural features of the interstitial rhombohedral α-boron-based B(C,O) phases and the data on the known carbides and boron suboxides allowed the characterization of the new phase.

Development of methods of X-ray diffraction analysis for determining the composition and structure of sillenite-family crystals

The crystal structure of a 12-layer tounkite-like mineral of the cancrinite group was determined for the first time by single-crystal X-ray diffraction analysis (the unit-cell parameters are a = 12.757 Å, c = 32.211 Å). The structure was refined in the space group P3 to R = 0.035 using 3834 reflections with | F| > 2σ(F). Si and Al atoms occupy tetrahedral framework positions in an ordered fashion. The average distances in the tetrahedra are 〈Si-O〉 = 1.611 Å and 〈Al-O〉 = 1.723 Å. The stacking sequence of the layers is described as CACACBCBCACB, where A, B, and C are six-membered rings arranged around the [2/3 1/3 z], [1/3 2/3 z], and [0 0 z] axes, respectively. In the structure of the mineral, the columns along the [0 0 z] axis are composed of cancrinite cages. The columns along the [2/3 1/3 z] and [1/3 2/3 z] axes contain alternating cancrinite, bystrite, and liottite cages.

Isotropic lazurite: A cubic single crystal with an incommensurate three-dimensional modulation of the structure

This work begins a series of papers aimed at studying the defect structure of nonstoichiometric phases R1 − yCayF3 − y with a tysonite-type (LaF3) structure. In the single-crystal structure of Y0.715Ca0.285F2.715 with a tysonite-type small unit cell (sp. gr. P63/mmc, a = 3.9095(2) Å, c = 6.9829(2) Å; Z = 2; Rw = 2.16%), the displacements of Y3+ cations and F2− anions from 63 symmetry axes were observed for the first time. The X-ray diffraction pattern shows weak satellites insufficient for structural calculations. The LaF3 structure type is stabilized up and down on the temperature scale due to anion vacancies and the symmetrizing effect of Ca2+ cations lying on 63 symmetry axes. At 120°C the fluoride-ion conductivity in the nonstoichiometric phase Y0.715Ca0.285F2.715 is five orders of magnitude higher than that in the stoichiometric phase β-YF3. The transition to a superionic state is caused by a deviation from stoichiometry and is not associated with reconstructive phase transformation.

Incommensurately modulated twin structure of nyerereite Na1.64K0.36Ca(CO3)2

The structures of the ɛ-FeOOH, ɛ-FeOOD, and β-GaOOH phases, which belong to the InOOH structure type (the distorted TiO2 structure type), are determined using single-crystal X-ray diffraction analysis. The measurements are performed on Xcalibur CCD and CAD-4F diffractometers. The calculations are carried out in space group P21nm with the JANA2000 program. The crystals are twinned and form aggregates related by the rotation around the b axis through an angle close to 62°. In the same crystals, the merohedral twinning is characterized by the rotation around the c axis through an angle of 180°. The alternation of these twin domains in the bulk of the crystal determines the corresponding disordering of the hydrogen positions.

Structural features of single crystals of LuB12 upon a transition to the cage-glass phase

The defect structure of crystals of as-grown nonstoichiometric tysonite (LaF3 type) La1 − ySryF3 − y phase (y = 0, 0.05, 0.07, and 0.15) has been investigated by X-ray diffraction and neutron diffraction. A concentration-driven structural transition from the β-La1 − ySryF3 − y modification to the α-La1 − ySryF3 − y modification in the range y = 0.05–0.10 has been observed for the first time. This transition correlates with the maximum of fluorine-ion conductivity (y = 0.05 ± 0.02) and the maximum in the melting curve (y = 0.07 ± 0.03). β-LaF3 and β-La0.95Sr0.05F2.95 crystals belong to the trigonal system (sp. gr.