Four-circle X-ray Diffractometer Research Articles

CRISTAL-ITE: a single-crystal X-ray diffractometer scale model for scientific dissemination

This article presents the design and manufacture of an automated scale model of a four-circle single-crystal X-ray diffractometer that can be used for scientific dissemination. The purpose of this device is to reach out to the wider public and students to introduce them in an entertaining way to one of the laboratory apparatuses to which they do not usually have access, to talk to them about crystallography in the broadest sense, to develop concepts in various fields of science and technology, and to initiate interest and discussions. The main technical aspects of the project are described, with the expectation that such an approach could be useful to anyone involved in scientific dissemination and could be developed for other laboratory equipment and other disciplines. This kind of device can also be the subject of scientific and technological projects in close collaboration with educational institutions.

Влияние отжига в ферромагнитном состоянии на структуру сплава железа с 18 at.% галлия

AbstractThe atomic structure of the iron–gallium alloy containing 18 at % Ga has been studied by X-ray diffraction. The samples were annealed in the paramagnetic ( T > T _C) and ferromagnetic ( T < T _C) state. In the first case, the structural state was fixed by quenching from the annealing temperature into water; in the second case, the structural state was obtained by slow cooling. The structural studies of the single-crystal samples were conducted on a four-circle X-ray diffractometer at room temperature. From the X-ray diffraction data, it follows that the alloy, independently on the heat treatment, contains B 2 clusters, i.e., locally ordered regions with the CsCl-type structure observed in alloys of iron with silicon (to 10 at % Si) and aluminum (7 at % Al) before. In addition to the B 2‑clusters, regions with the D 0_3 short-range order are observed in the quenched sample; the sizes of these regions significantly increases after annealing in the ferromagnetic state, i.e., a long-range order forms. The relation of the fine structural changes in the alloy due to various heat treatments with its magnetoelastic and magnetostriction properties is discussed.

Effect of Annealing in a Ferromagnetic State on the Structure of an Fe–18 at % Ga Alloy

The atomic structure of the iron–gallium alloy containing 18 at % Ga has been studied by X-ray diffraction. The samples were annealed in the paramagnetic (T > TC) and ferromagnetic (T < TC) state. In the first case, the structural state was fixed by quenching from the annealing temperature into water; in the second case, the structural state was obtained by slow cooling. The structural studies of the single-crystal samples were conducted on a four-circle X-ray diffractometer at room temperature. From the X-ray diffraction data, it follows that the alloy, independently on the heat treatment, contains B2 clusters, i.e., locally ordered regions with the CsCl-type structure observed in alloys of iron with silicon (to 10 at % Si) and aluminum (7 at % Al) before. In addition to the B2‑clusters, regions with the D03 short-range order are observed in the quenched sample; the sizes of these regions significantly increases after annealing in the ferromagnetic state, i.e., a long-range order forms. The relation of the fine structural changes in the alloy due to various heat treatments with its magnetoelastic and magnetostriction properties is discussed.

Short-Range Order in α-FeAl Soft Magnetic Alloy

The atomic structure of iron–aluminum alloy samples containing about 7 at % of aluminum (α region of the phase diagram) was investigated by X-ray diffraction. The samples were annealed in the paramagnetic (T > TC) and ferromagnetic (T < TC) states. In the first case, the structural state was fixed by quenching from the annealing temperature in water, and, in the second case, by slow cooling. Diffraction patterns of single-crystal samples were taken on an X-ray four-circle diffractometer. It is shown that local ordering, regardless of the prehistory of a sample, is a combination of B2-phase clusters (the CsCl type structure), which were previously found in iron–silicon alloys with Si content up to 10%, and small regions with D03 short-range order. The former consist of two B2-cells having a common face, while the latter consist predominantly of one unit cell of the D03-phase. Within the accuracy of the experiment, no significant difference in the structural states in the paramagnetic and ferromagnetic phases was observed.

Ближний порядок в магнитомягком сплаве alpha-FeAl

AbstractThe atomic structure of iron–aluminum alloy samples containing about 7 at % of aluminum (α region of the phase diagram) was investigated by X-ray diffraction. The samples were annealed in the paramagnetic ( T &gt; ^T_ C ) and ferromagnetic ( T &lt; T _ C ) states. In the first case, the structural state was fixed by quenching from the annealing temperature in water, and, in the second case, by slow cooling. Diffraction patterns of single-crystal samples were taken on an X-ray four-circle diffractometer. It is shown that local ordering, regardless of the prehistory of a sample, is a combination of B 2-phase clusters (the CsCl type structure), which were previously found in iron–silicon alloys with Si content up to 10%, and small regions with D 0_3 short-range order. The former consist of two B 2-cells having a common face, while the latter consist predominantly of one unit cell of the D 0_3-phase. Within the accuracy of the experiment, no significant difference in the structural states in the paramagnetic and ferromagnetic phases was observed.

Polytypism of cronstedtite from Nižná Slaná, Slovakia

Cronstedtite, (Fe 2 + 3− x Fe 3 + x )(Si 2 − x Fe 3 + x )O 5 (OH) 4 , was found in the Mano metasomatic siderite deposit near Nižna Slana, Slovakia. The deposit is hosted in Early Palaeozoic rocks of the Gemeric Superunit. Cronstedtite occurs mostly as slim, up to 2.5-mm trigonal pyramids in drusy cavities in the octahedral or cubo-octahedral crystals of pyrite in quartz veins. Separated crystals (21 altogether, including fragments of larger crystals) were checked on the four-circle X-ray diffractometer with area detector. From user-defined pre-experiments, the −2 h h l , h h l , − h 2 h l , h 0 l , 0 k l , − h h l (in hexagonal indices) precession-like images of reciprocal lattice planes were constructed using the diffractometer software. The OD (ordered–disordered) subfamilies (Bailey’s groups) and polytypes were identified from the reflection distribution along −2 1 l /1 1 l /12 l and 1 0 l /0 1 l /−1 1 l rows (hexagonal indices), respectively. Some selected crystals were further studied by electron probe micro-analysis (EPMA). Almost all crystals studied belong to the A group. The most common polytype is 3 T , occurring either as the only one in crystals, or intergrown with 1 M polytype. Most of 3 T crystals are twinned by reticular merohedry interchanging the obverse/reverse settings of the rhombohedral subfamily structure. This twinning affects predominantly bottom and central parts, but not apices of crystals. In a rare, rounded tabular, and strongly disordered D-group crystal, the 2 H 1 and traces of the 2 H 2 polytypes were recognized. Besides the major Si and Fe contents, small amounts of Cl (0.02–0.06 apfu ) and mainly of S (up to 0.11 apfu ) were detected by EPMA.

Polytypism of cronstedtite from Pohled, Czech Republic

Cronstedtite (Fe2+3− x Fe3+ x )(Si2− x Fe3+ x )O5(OH)4, was found in an active quarry near Pohled, Czech Republic, in the Monotone Series of Moravian Moldanubicum near the eastern edge of the Moldanubian pluton. Rare, up to 3 mm large crystals occur in a vuggy, 3 cm thick hydrothermal pyrite vein, penetrating a migmatized paragneiss near the contact with two-mica granite of the Eisgarn type. Separated crystals (43 altogether) were studied using a four-circle X-ray diffractometer with a CCD area detector. From 217 frames per user-defined pre-experiment, the -2 hhl, hhl, -h 2 hl, h 0 l , 0 kl, -hhl (in hexagonal indices) precession-like reciprocal lattice sections were constructed using the diffractometer software. The OD subfamilies (Bailey’s groups) and polytypes were identified from the reflection distribution along -21 l /11 l /-12 l and 10 l /01 l /-11 l rows (hexagonal indices), respectively. Selected crystals were further studied by electron-microprobe analysis (EPMA). Three types of crystals were distinguished: 1) mixed 2 H 1 + 2 H 2 crystals (group D) with the 2 H 1 polytype dominant in most specimens [lattice parameters of both polytypes a = 5.5002(4), c = 14.195(1) A, space groups: P 63 cm (2 H 1), P 63 (2 H 2)]; 2) the new non-MDO polytype 6 T 2 (group A) [ a = 5.4976(3), c = 42.601(1) A, space group P 31]; 3) mixed 3 T + 1 M (group A) crystals, [ a = 5.4975(4), c = 21.262(1) A, P 31 (3 T ), a = 5.4967(6), b = 9.5214(9) c = 7.3216(8) A, β = 104.52(1)°, Cm (1 M )]. Rare twins by reticular merohedry were identified in one 6 T 2 and one 3 T + 1 M crystal. Possible accessories of the 2 M 1 and some unknown polytypes were detected in some of the 6 T 2 and 2 H 1 + 2 H 2 crystals, respectively. The EPMA studies revealed that the 6 T 2 polytype is relatively Fe-poor (in the formula above, average x = 0.73), 3 T +1 M polytypes Fe-rich (average x = 0.77), and 2 H 1 (+ 2 H 2) polytypes have intermediate composition ( x = 0.72–0.78). Minor contents of chlorine were determined for 2 H 1 (+ 2 H 2) polytypes (up to 0.015 apfu ) and 3 T +1 M polytypes (up to 0.009 apfu ).

Crystal Structure and Magnetic Properties of New Cubic Quaternary Compounds RT2Sn2Zn18 (R = La, Ce, Pr, and Nd, and T = Co and Fe)

The new cubic quaternary intermetallic compounds RT2Sn2Zn18 (R = La, Ce, Pr, and Nd, and T = Co and Fe) were synthesized by the mixture-metal flux method using Zn and Sn. The crystal structure was investigated by powder X-ray diffraction and with a four-circle X-ray diffractometer using single crystals. The space group of the compounds is \(Fd\bar{3}m\) (No. 227). The rare-earth atom is at the cubic site which is the center of a cage composed of Zn and Sn atoms. The crystal structure is the same as the CeCr2Al20-type crystal structure except the atoms at the 16c site, i.e., the Zn atoms at the 16c site are completely replaced by Sn atoms, indicating that the compounds are crystallographically new ordered quaternary compounds. The lattice parameter a and the physical properties of the magnetic susceptibility χ, the magnetization M, and the specific heat C of these cubic caged compounds were investigated. LaCo2Sn2Zn18 and LaFe2Sn2Zn18 are enhanced Pauli paramagnets that originate from the Co and Fe itinerant 3d electrons. CeCo2Sn2Zn18 and CeFe2Sn2Zn18 are also enhanced Pauli paramagnets that originate from both the 3d electrons and Ce 4f electrons. PrCo2Sn2Zn18 and PrFe2Sn2Zn18 are nonmagnetic materials with huge values of C divided by temperature, which indicates that the ground state of Pr ions is a non-Kramers’ doublet. NdCo2Sn2Zn18 and NdFe2Sn2Zn18 are magnetic materials with the Néel temperatures of 1.0 and 3.8 K, respectively. All eight compounds have large magnetic moments of Co/Fe in the paramagnetic temperature region, and thus their magnetic moments are inferred to be magnetically frustrating owing to the pyrochlore lattice in the low-temperature region.

Description and crystal structure of albrechtschraufite, MgCa4F2[UO2(CO3)3]2⋅17-18H2O

Albrechtschraufite, MgCa4F2[UO2(CO3)3]2⋅17-18H2O, triclinic, space group Pī, a = 13.569(2), b = 13.419(2), c = 11.622(2) A, α = 115.82(1), β = 107.61(1), γ = 92.84(1)° (structural unit cell, not reduced), V = 1774.6(5) A3, Z = 2, D c = 2.69 g/cm3 (for 17.5 H2O), is a mineral that was found in small amounts with schrockingerite, NaCa3F[UO2(CO3)3](SO4)⋅10H2O, on a museum specimen of uranium ore from Joachimsthal (Jachymov), Czech Republic. The mineral forms small grain-like subhedral crystals (≤ 0.2 mm) that resemble in appearance liebigite, Ca2[UO2(CO3)3]⋅ ~ 11H2O. Colour pale yellow-green, luster vitreous, transparent, pale bluish green fluorescence under ultraviolet light. Optical data: Biaxial negative, nX = 1.511(2), nY = 1.550(2), nZ = 1.566(2), 2 V = 65(1)° (λ = 589 nm), r < v weak. After qualitative tests had shown the presence of Ca, U, Mg, CO2 and H2O, the chemical formula was determined by a crystal structure analysis based on X-ray four-circle diffractometer data. The structure was later on refined with data from a CCD diffractometer to R1 = 0.0206 and wR2 = 0.0429 for 9,236 independent observed reflections. The crystal structure contains two independent [UO2(CO3)3]4− anions of which one is bonded to two Mg and six Ca while the second is bonded to only one Mg and three Ca. Magnesium forms a MgF2(Ocarbonate)3(H2O) octahedron that is linked via the F atoms with three Ca atoms so as to provide each F atom with a flat pyramidal coordination by one Mg and two Ca. Calcium is 7- and 8-coordinate forming CaFO6, CaF2O2(H2O)4, CaFO3(H2O)4 and CaO2(H2O)6 coordination polyhedra. The crystal structure is built up from MgCa3F2[UO2(CO3)3]⋅8H2O layers parallel to (001) which are linked by Ca[UO2(CO3)3]⋅5H2O moieties into a framework of the composition MgCa4F2[UO2(CO3)3]⋅13H2O. Five additional water molecules are located in voids of the framework and show large displacement parameters. One of the water positions is partly vacant, leading to a total water content of 17-18H2O per formula unit. The MgCa3F2[UO2(CO3)3]⋅8H2O layers are pseudosymmetric according to plane group symmetry cmm. The remaining constituents do not sustain this pseudosymmetry and make the entire structure truly triclinic. A characteristic paddle-wheel motif Ca[UO2(CO3)3]4Ca relates the structure of albrechtschraufite partly to that of andersonite and two synthetic alkali calcium uranyl tricarbonates.

Spin State Transition Studied by Means of Optical Microscope

We have tested a new method which allows assigning the spin state of the spin crossover (SCO) crystal in-situ during the diffraction experiment. The method is based on the analysis of change of the colour of the SCO compounds. We have found that the off-line setup in transmission geometry is reliable in assigning the magnitude of high spin molecules fraction (γHS) and the character (one step, many steps, histeresis) of the SCO transition. Later on, this method has been used in the in-situ measurements directly on X-ray four-circle diffractometer.

CARBOBYSTRITE, Na8[Al6Si6O24](CO3){middle dot}4H2O, A NEW CANCRINITE-GROUP MINERAL SPECIES FROM THE KHIBINA ALKALINE MASSIF, KOLA PENINSULA, RUSSIA: DESCRIPTION AND CRYSTAL STRUCTURE

Carbobystrite, ideally Na 8 [Al 6 Si 6 O 24 ](CO 3 )·4H 2 O, trigonal, a 12.6678(5), c 10.3401(4) A, V 1437.0(2) A 3 , c:a = 0.8162, space group P 31 c , Z = 2, R = 0.0271 (for 4861 observed reflections collected with a four-circle X-ray diffractometer), is a new cancrinite-group mineral species from Mount Koashva, Khibina alkaline massif, Kola Peninsula, Russia. It formed in a pegmatitic environment. Associated minerals are: microcline, sodalite, megakalsilite, natrolite, pectolite, aegirine, natrite, nacaphite, vitusite-(Ce), fluorcaphite, belovite-(Ce), umbite, lemmleinite-K, lomonosovite, lovozerite, phlogopite, sphalerite and galena. The mineral was found in only one hand specimen of pegmatite as a corroded irregularly shaped grain about 3 mm across, intergrown with sodalite, megakalsilite and natrite. It is transparent, colorless with a white streak, a vitreous luster, and fluoresces pale yellow under ultraviolet light. Carbobystrite has a Mohs hardness of 6, is brittle with a conchoidal fracture, and has no cleavage. The calculated density is 2.366 g/cm 3 . Carbobystrite is uniaxial negative, non-pleochroic, ω 1.500(2), e 1.488 (2). The strongest six reflections in the X-ray powder-diffraction pattern [ d in A(I)( hkl )] are: 4.689(100)(012), 3.249(100)(132, 122), 6.378(80) (120), 2.661(80)(041, 123, 133), 3.867(70)(131, 121), and 3.664(70)(030). An electron-microprobe analysis gives Na 2 O 22.66, K 2 O 1.75, SiO 2 35.74, Al 2 O 3 30.42, CO 2 4.37, H 2 O 6.26, sum 101.20 wt.%, with CO 2 and H 2 O calculated from structural data. The empirical formula (based on O = 30.5 atoms per formula unit) is (Na 7.40 K 0.38 ) ∑7.78 (Al 6.04 Si 6.02 ) ∑12.06 O 24 (CO 3 )·3.5H 2 O; the simplified formula is Na 8 [Al 6 Si 6 O 24 ](CO 3 )·4H 2 O. The name carbobystrite denotes the compositional relation between the new mineral and bystrite, (Na,K) 7 Ca[Al 6 Si 6 O 24 ](S) 1.5 ·H 2 O; they are related by the substitution Na + + (CO 3 ) 2− + 2.5H 2 O → Ca 2+ + (S 2− ) 1.5 . The framework of Si,Al–O tetrahedra can be described as an ABAC stacking sequence. In the crystal structure, there are two LOSOD cages, and two e (cancrinite) cages per unit cell, giving a maximum of two (CO 3 ) groups and six H 2 O groups for the LOSOD-type cages and two H 2 O groups for the cancrinite cages, respectively. This is the first complex-sequence cancrinitegroup mineral with (CO 3 ) groups in cages larger than the cancrinite cages. Carbobystrite suggests a new series of carbonate equivalents of all known complex sequences in the cancrinite group.

Formalism for the determination of intermediate stress gradients using X-ray diffraction

A method is outlined that allows the determination of one-dimensional stress gradients at length scales greater than 0.2 mm. By using standard four-circle X-ray diffractometer equipment and simple aperture components, length resolutions down to 0.05 mm in one direction can be achieved through constant orientation of a narrow, line-shaped beam spot. Angle calculations are given for the adjustment of goniometer angles, and for the effective azimuth and tilt of the scattering vector for general angle settings in a four-circle goniometer. The latter is necessary for the computation of stresses from lattice strain measurements.

Synthesis, molecular structure, non-isothermal decomposition kinetics and adiabatic time to explosion of 3,3-dinitroazetidinium 3,5-dinitrosalicylate

Abstract The title compound 3,3-dinitroazetidinium (DNAZ) 3,5-dinitrosalicylate (3,5-DNSA) was prepared and the crystal structure has been determined by a four-circle X-ray diffractometer. The thermal behavior of the title compound was studied under a non-isothermal condition by DSC and TG/DTG techniques. The kinetic parameters were obtained from analysis of the TG curves by Kissinger method, Ozawa method, the differential method and the integral method. The kinetic model function in differential form and the value of E a and A of the decomposition reaction of the title compound are f(α)=4α3/4, 130.83 kJ mol−1 and 1013.80s−1, respectively. The critical temperature of thermal explosion of the title compound is 147.55 °C. The values of ΔS ≠, ΔH ≠ and ΔG ≠ of this reaction are −1.35 J mol−1 K−1, 122.42 and 122.97 kJ mol−1, respectively. The specific heat capacity of the title compound was determined with a continuous C p mode of mircocalorimeter. Using the relationship between C p and T and the thermal deco...

X-ray reciprocal space maps and x-ray scattering topographic observation of GaN layer on GaAs (001) in plasma-assisted molecular beam epitaxy

We have characterized plasma-assisted N+ molecular beam epitaxy-grown polymorphous GaN epitaxial layer on GaAs by x-ray reciprocal mapping using four-circle x-ray diffractometer and a personal computer controlled x-ray scattering topography system by ourselves. x-ray reciprocal mapping indicates that GaN wurtzite epitaxial film was grown along only [1¯1¯1] direction. While GaN wurtzite and zinc-blende crystals were contracted along the surface normal, those of lattice constants were expanded along lateral direction. The values of expansion were larger than our instrumental resolution. The lateral expansion rate of lattice constants in GaN wurtzite was larger than that in GaN zinc blende. It was found that zinc-blende phase was unevenly distributed, but wurtzite one was uniformly distributed by growth condition.

Comparison of two molten flux process for the elaboration of textured PZT thin plates

In this paper, we describe a new protocol for the elaboration of textured PZT thin plates. This protocol is based on three steps: (i) powder synthesis, (ii) tape casting/lamination in green state and (iii) sintering/densification. Powder synthesis is operated through a specific molten flux method, which in optimised conditions allows the crystallisation of coarse and cubic shape grains of PZT. The powder is extracted from the flux by acidic attack, washing and filtration. It is used as raw material to elaborate a slip with organic media in order to achieve thick tapes that exhibit preferred orientations of the PZT phase. The crystallographic textures are measured on a four-circle X-ray diffractometer and determined using the so-called “combined approach” that uses Rietveld and orientation distribution function refinements.

Syntheses, Molecular Structure and Thermodynamic Properties of 3-Nitro-1,2,4-triazol-5-one Europium Complex [Eu(NTO)3(H2O)5]·5H2O

3-Nitro-1,2,4-triazol-5-one (NTO) europium complex of [Eu(NTO)3(H2O)5]·5H2O was synthesized by mixing the aqueous solution of lithium 3-nitro-1,2,4-triazol-5-onate and the dilute nitric acid solution of europium oxide. The title complex was characterized by elemental analysis and IR spectra. The single crystal structure was determined by a four-circle x-ray diffractometer. The title complex is monoclinic with space group P21/n and unit cell parameters of a = 1.8720(2) nm, b = 0.6548(3) nm, c = 1.9323(3) nm and β = 95.33(1)°. The coordination geometry around the europium ion is a distorted dodecahedron and there are five crystalline water molecules to form the stable structure of the crystal. From measurements of the enthalpy of solution in water at 298.15 K, the standard enthalpy of formation, lattice enthalpy and lattice energy have been determined as -(3798.6 ± 3.7), −4488.4 and −4452.4 kJ·mol−;1, respectively.

Epitaxial Growth and Structural Characterization of Transparent Conducting ZnO:Al Thin Film Deposited on GaN Substrate by rf Magnetron Sputtering

Transparent conducting oxide Al-modified (2 wt.%) ZnO (AZO) was deposited on a GaN/Al2O3 substrate by rf magnetron sputtering at a substrate temperature of 400 ◦C. With the help of a small lattice mismatch (about 1.9 %) and structural similarity (hexagon on hexagon epitaxy), the AZO film was epitaxially grown on the GaN substrate. This was investigated by four-circle X-ray diffractometer by using monochromatized Cu Kα1 radiation. The AZO film was well oriented to the lattice of GaN on the a − b plane. This was confirmed by phi-scan measurements of (103) reflection of the AZO layer and of (103) reflection of the GaN substrate under fixed conditions of ψ = 31.66◦ (2θ = 62.858◦) and ψ = 32.04◦ (2θ = 63.435◦), respectively. The AZO film showed smooth surface roughness (Ra: ∼50 A) and uniformly distributed grains. To investigate the optical transparency, the transmittance spectrum of the AZO/GaN-stacked film was characterized and showed a high transmittance (over 85 %) in the visible spectral range. The resistivity and carrier concentration of the AZO/GaN film, under varying annealing temperatures, were analyzed by Hall measurement and showed a maximal value of 2.38 × 10−4 Ω·cm and 2.57 × 10 cm−3, respectively, for the 400 ◦C-deposited film.

Preparation, crystal structure and thermal decomposition kinetics of 1-(2,4-dinitrophenyl)azo-1-nitrocyclohexane

A new three-nitro-group compound of 1-(2,4-dinitrophenyl)azo-1-nitrocyclohexane was prepared by the reaction of cyclohexanone-2,4-dinitrophenylhydrazine with nitric oxide at ambient temperature. The single crystal structure has been determined by a four-circle X-ray diffractometer. The compound is monoclinic with space group P2(1)/ c and unit-cell parameters a=11.300(2) Å, b=12.993(2) Å, c=10.155(1) Å, β=98.33(1) o, F(000)=672, the unit-cell volume V=1475.2(5) Å 3, the molecule number in one unit-cell Z=4, the absorption coefficient μ=1.19 cm −1, the calculated density D c=1.456 g cm −3. The exothermic decomposition reaction kinetics of the compound has been studied by DSC. The kinetic model function in differential form, apparent activation energy and pre-exponential constant of this reaction are (3/4)(1−α)[−ln(1−α)] 1/4, 123.88 kJ mol −1 and 10 11.49 s −1, respectively. The critical temperature of thermal explosion of the title compound is 161.15 oC and the entropy of activation ( Δ S ≠ ) , enthalpy of activation ( Δ H ≠ ) , and free energy of activation ( Δ G ≠ ) are −34.16 J mol −1 K −1, 115.7, and 130.48 kJ mol −1, respectively.

Cooperative Displacements of Ba2+ Ions in the Incommensurate Structural Phase of Piezoelectric Layer Compound BaMnF4

Structural properties of BaMnF 4 has been studied in the incommensurate phase (ICP) below about 250 K by X-ray diffraction. The ICP structure has a unit cell of N a p ×2 b p ×2 c p ; N ∼5, where a p , b p and c p mean lattice constants at room-temperature commensurate phase (CP). The structure is determined at about 200 K in addition to that at room temperature, by using a four-circle X-ray diffractometer. The large distortion of each MnF 6 octahedron, which jointly owns two F - ions along the a -axis and a F - ion along the c -axis with a neighbor octahedron, is roughly similar in the ICP phase with those in the CP phase. In the ICP phase, the MnF 6 octahedra show different tilting-scheme between nearest-neighboring two-dimensional MnF 6 octahedra networks (folding screens), which are stacked along the b -axis and alternatively displaced each other with a glide vector of (0,1/4,1/4) in the unit cell of the ICP phase. There are two types of folding screens which are stacked along the b p -axis alternately...

Preparation, crystal structure, thermal decomposition mechanism and thermodynamic properties of [Co(H 2O) 6](NTO) 2·2H 2O

The single crystal of cobalt compound of 3-nitro-1,2,4-triazol-5-one (NTO) ([Co(H 2O) 6](NTO) 2·2H 2O) was prepared and the crystal structure has been determined by a four-circle X-ray diffractometer. The compound is monoclinic with space group Cc and unit cell parameters of a=2.3163 (2) nm, b=0.6451 (1) nm, c=1.4123 (1) nm, β=123.96 (1)°, V=1.7504 (3) nm 3 and Z=4. Based on the thermal analysis, the thermal decomposition mechanism of [Co(H 2O) 6](NTO) 2·2H 2O has been derived. From measurements of the enthalpy of solution in water at 298.15 K, the standard enthalpy of formation, lattice enthalpy and lattice energy have been determined as −(2594.7±4.5), −2753.19, and −2718.19 kJ mol −1, respectively.