X-ray Powder Diffractograms Research Articles

Computation of X-ray powder diffractograms of cement components and its application to phase analysis and hydration performance of OPC cement

The importance of computed X-ray diffraction patterns of various polymorphs of alite ( ${\bf \emph{M}_{3}, \emph{T}_{1}, \emph{R}}$ ), belite ( $\boldsymbol{\beta}$ , $\boldsymbol{\gamma}$ ), aluminate (cubic, orthorhombic), aluminoferrite, gypsum and hemihydrate in the quantitative phase analysis of cement and its early stage hydration performance is highlighted in this work with three OPC samples. The analysis shows that the predominant silicate phases present in all the samples are ${\bf \emph{M}_{3}}$ -alite phase and $\boldsymbol{\beta}$ -belite phase, respectively. Both cubic and orthorhombic phases of C 3 A, brownmillerite, gypsum and hemihydrates are present at different levels. Quantitative phase analysis of cement by Rietveld refinement method provides more accurate and comprehensive data of the phase composition compared to Bogue method. The comparative hydration performance of these samples was studied with ${\bf \emph{w/c}}$ ratio, 0·5 and the results are interpreted in the light of difference in phase compositions viz. $\boldsymbol{\beta}$ -C 2 S/C 3 S ratio, fraction of finer cement particles present in the samples and theoretical modeling of C 3 S hydration.

Equilibrated High-Density Amorphous Ice and Its First-Order Transition to the Low-Density Form

We investigate the downstroke transition from high- (HDA) to low-density amorphous ice (LDA) at 140 (H(2)O) and 143 K (D(2)O). The visual observation of sudden phase separation at 0.07 GPa is evidence of the first-order character of the transition. Powder X-ray diffractograms recorded on chips recovered from the propagating front show a double halo peak indicative of the simultaneous presence of LDA and HDA. By contrast, chips picked from different parts of the sample cylinder show either HDA or LDA. Growth of the low-density form takes place randomly somewhere inside of the high-density matrix. The thermal stability of HDA against transformation to LDA at ambient pressure significantly increases with decreasing recovery pressure and reaches its maximum at 0.07 GPa. A sample decompressed to 0.07 GPa is by ~17 K more stable than an unannealed HDA sample. An increasingly relaxed nature of the sample is also evident from the progressive disappearance of the broad calorimetric relaxation exotherm, preceding the sharp transition to LDA. Finally, we show that two independent thermodynamic paths lead to a very similar state of (relaxed) HDA at 140 K and 0.2 GPa. We argue that these observations imply an equilibrated nature of the amorphous sample in the pressure range of p ≲ 0.2 GPa and speculate that the observation of macroscopic phase separation involves two ultraviscous liquid phases at 140 K. This supports the scenario of a first-order liquid-liquid transition in bulk water.

Formation of solid solutions between racemic and enantiomeric citalopram oxalate

The X-ray powder diffractograms of racemic citalopram oxalate and (S)-citalopram oxalate are very similar, but the melting point of the racemate is higher than that of the pure enantiomer. The higher melting point indicates that the racemate is a racemic compound, rather than a conglomerate. The crystal structure of the enantiomer contains two molecules of (S)-citalopram in the asymmetric unit. The conformation of the two molecules is different but they approximate mirror images of each other if the aromatic groups are interchanged. The crystal structure of the racemate is essentially isostructural with that of the enantiomer, having almost the same cell parameters but containing a crystallographic inversion centre that is not retained in the enantiomer structure. The closely-comparable crystal structures permit solid solutions to be formed between racemic and enantiomeric citalopram oxalate. Phase diagrams of the (R)-citalopram and (S)-citalopram oxalate system are constructed, and they show that solid solutions are formed at all ratios of the two enantiomers.

Preformulation Studies of Zidovudine Derivatives: Acid Dissociation Constants, Differential Scanning Calorimetry, Thermogravimetry, X-Ray Powder Diffractometry and Aqueous Stability Studies

As part as of the preformulation studies of new 5′-OH derivatives of zidovudine, compounds 2–6, their acid dissociation constants, Differential Scanning Calorimetry (DSC) and Thermogravimetry (TG) curves, X-Ray Powder diffractograms and aqueous stability are reported. A sensitive technique such as differential scanning potentiometry was used to determine the pKa constants of the above mentioned compounds. In addition, pKa values were calculated from theoretical methods, and no significant differences with those of experimental ones were observed. X-Ray Powder Diffractometry data demonstrated that compounds 2–4 were crystalline while 5 and 6 were amorphous. DSC analysis indicated that all of them presented an exothermic decomposition peak above 150 °C which is accompanied by a weight loss in the respective TG curves. The stability of these compounds in aqueous medium at different pH values was investigated, using a validated High Performance Liquid Chromatography (HPLC) method, which demonstrated to be rapid, selective, sensitive, accurate and stability-indicating. Good recovery, linearity and precision were also achieved. For all compounds the aqueous hydrolysis followed a pseudo-first-order kinetics, depending on pH and the union existing between AZT and the associate moiety. The hydrolysis was catalyzed by hydroxide ion in the 7.4–13.2 pH range, while all compounds exhibited pH-independent stability from acidic to neutral media (pHs 1.0–7.4).

The Influence of Milling on the Dissolution Performance of Simvastatin.

Particle size reduction is a simple means to enhance the dissolution rate of poorly water soluble BCS-class II and IV drugs. However, the major drawback of this process is the possible introduction of process induced disorder. Drugs with different molecular arrangements may exhibit altered properties such as solubility and dissolution rate and, therefore, process induced solid state modifications need to be monitored. The aim of this study was two-fold: firstly, to investigate the dissolution rates of milled and unmilled simvastatin; and secondly, to screen for the main milling factors, as well as factor interactions in a dry ball milling process using simvastatin as model drug, and to optimize the milling procedure with regard to the opposing responses particle size and process induced disorder by application of a central composite face centered design. Particle size was assessed by scanning electron microscopy (SEM) and image analysis. Process induced disorder was determined by partial least squares (PLS) regression modeling of respective X-ray powder diffractograms (XRPD) and Raman spectra. Valid and significant quadratic models were built. The investigated milling factors were milling frequency, milling time and ball quantity at a set drug load, out of which milling frequency was found to be the most important factor for particle size as well as process induced disorder. Milling frequency and milling time exhibited an interaction effect on the responses. The optimum milling settings using the maximum number of milling balls (60 balls with 4 mm diameter) was determined to be at a milling frequency of 21 Hz and a milling time of 36 min with a resulting primary particle size of 1.4 μm and a process induced disorder of 6.1% (assessed by Raman spectroscopy) and 8.4% (assessed by XRPD), at a set optimization limit of < 2 μm for particle size and < 10% for process induced disorder. This optimum was tested experimentally and the process induced disorder was determined to be 6.9% (± 2.2) by Raman spectroscopy and 7.8% (± 2.3) by XRPD. Subsequent intrinsic dissolution testing revealed that the process induced disorder was negligible with regard to the dissolution rate. The predicted primary particle size of 1.4 μm could be confirmed experimentally, but due to agglomeration of the primary particles a dissolution rate advantage was not shown, highlighting the importance of dissolution testing at an early stage of drug development.

Subglacial Hydrothermal Alteration Minerals in Jökulhlaup Deposits of Southern Iceland, with Implications for Detecting Past or Present Habitable Environments on Mars

Jökulhlaups are terrestrial catastrophic outfloods, often triggered by subglacial volcanic eruptions. Similar volcano-ice interactions were likely important on Mars where magma/lava may have interacted with the planet's cryosphere to produce catastrophic floods. As a potential analogue to sediments deposited during martian floods, the Holocene sandurs of Iceland are dominated by basaltic clasts derived from the subglacial environment and deposited during jökulhlaups. Palagonite tuffs and breccias, present within the deposits, represent the primary alteration lithology. The surface abundance of palagonite on the sandurs is 1-20%. X-ray diffraction (XRD) analysis of palagonite breccias confirms a mineral assemblage of zeolites, smectites, low-quartz, and kaolinite. Oriented powder X-ray diffractograms (< 2 microm fraction) for palagonite breccia clasts and coatings reveal randomly ordered smectite, mixed layer smectite/illite, zeolites, and quartz. Visible light-near infrared (VNIR) and shortwave infrared (SWIR) lab spectroscopic data of the same palagonite samples show H2O/OH(-) absorptions associated with clays and zeolites. SWIR spectra derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images of the sandurs reveal Al-OH(-) and Si-OH(-) absorption features. The identified alteration mineral assemblage is consistent with low temperature (100-140 degrees C) hydrothermal alteration of basaltic material within the subglacial environment. These results suggest that potential martian analog sites that contain a similar suite of hydrated minerals may be indicative of past hydrothermal activity and locations where past habitable environments for microbial life may be found.

Synthesis, characterization and physicochemical properties of nanosized Zn/Mn oxides system

A series of pure and doped Li 2O–zinc/manganese mixed oxides was prepared by ceramic route at 400–1000 °C. The obtained solids have been characterized by the thermo-gravimetric analyzer (TGA), differential scanning calorimetry (DSC), X-ray powder diffractogram (XRD), infrared (IR), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) techniques. The catalytic behavior of pure and doped mixed solids was investigated using the decomposition reaction of H 2O 2 at 30–50 °C. The obtained results revealed that the solid state reaction between ZnO and Mn 2O 3 started at 500 °C yielding zinc manganite (ZnMn 2O 4) nanoparticles. The augmentation in the calcination temperature of the investigated solids up to 1000 °C for 4 h brought about complete conversion of unreacted oxides yielding ZnMn 2O 4 crystallites. By doping the system with Li 2O at different calcination temperatures, an enhancement of the formation of zinc manganite was observed. The products obtained by doping with Li 2O at different temperatures had less catalytic activity than the pure solids. The catalytic activity of pure and Li 2O-doped Zn/Mn mixed oxides system decreased by increasing the calcination temperature.

Crystal growth, structure and characterizations of a new semiorganic nonlinear optical material—β-Alanine zinc chloride

The title compound, β-alanine zinc chloride—a new semiorganic nonlinear optical crystal was grown by slow evaporation technique. Single crystals of β-alanine zinc chloride have been subjected to X-ray diffraction analysis to determine the crystal structure. The powder X-ray diffractogram of the crystal has also been recorded. The amount of carbon, nitrogen and hydrogen in the crystals was also estimated. Fourier Transform Infrared and Raman spectral measurements have been carried out on the grown crystals in order to identify the functional groups. The presence of hydrogen and carbon in the β-alanine zinc chloride was confirmed by using proton and carbon nuclear magnetic resonance spectral analyses. The percentage of zinc in the crystal was determined by atomic absorption spectroscopy. Optical behavior such as ultraviolet–vis–near infrared transmittance spectrum and second harmonic generation has been investigated. The mechanical strength and thermal behavior of the grown crystal have been analyzed.

Experimental and Theoretical Study of the Structures and Enthalpies of Formation of the Synthetic Reagents 1,3-Thiazolidine-2-thione and 1,3-Oxazolidine-2-thione

This paper reports an experimental and a theoretical study of the structures and standard (p(o) = 0.1 MPa) molar enthalpies of formation of the synthetic reagents 1,3-thiazolidine-2-thione [CAS 96-53-7] and 1,3-oxazolidine-2-thione [CAS 5840-81-3]. The enthalpies of combustion and sublimation were measured by rotary bomb combustion calorimetry, and the Knudsen effusion technique and gas-phase enthalpies of formation values at T = 298.15 K of (97.1 +/- 4.0) and -(74.4 +/- 4.6) kJ.mol(-1) for 1,3-thiazolidine-2-thione and 1,3-oxazolidine-2-thione, respectively, were determined. G3-calculated enthalpies of formation are in reasonable agreement with the experimental values. In the solid state, 1,3-thiazolidine-2-thione exists in two polymorphic forms (monoclinic and triclinic) and 1,3-oxazolidine-2-thione exits in the triclinic form. The isostructural nature of these compounds and comparison of their molecular and crystal structures have been analyzed. The experimental X-ray powder diffractograms have been compared with the calculated patterns from their structures for identification of the polymorphic samples used in this study. A comparison of our results with literature thermochemical and structural data for related compounds is also reported.

Synthesis and characterization of a new organic nonlinear optical crystal: l-Phenylalaninium maleate

l-Phenylalaninium maleate (abbreviated as LPM) chemical formula C 9H 12NO 2 +·C 4H 3O 4 −, a new organic nonlinear optical crystal was grown by slow evaporation technique. Transparent needle shaped crystal of dimensions 7 mm × 1 mm × 0.5 mm was obtained. Single crystals of LPM have been subjected to X-ray diffraction analysis to estimate the lattice parameters and the space group. The powder X-ray diffractogram of the crystal has been recorded and the reflections from various planes are identified. The XRD studies confirm the crystalline nature. The qualitative analysis on the crystal has been carried out using Fourier transform infrared (FTIR) and Fourier transform Raman (FTRaman) spectral measurements. The presence of hydrogen and carbon in the grown crystal was confirmed by using proton and carbon nuclear magnetic resonance (NMR) spectral analyses. Optical behaviour of the crystal was investigated using UV–vis spectroscopy. The thermal stability of the crystal was analysed with the aid of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The nonlinear optical (NLO) property of the crystal was tested by Nd:YAG laser source.

Increased Solubility, Dissolution and Physicochemical Studies of Curcumin- Polyvinylpyrrolidone K-30 Solid Dispersions

Solid dispersions (SD) of curcumin- polyvinylpyrrolidone in the ratio of 1:2, 1:4, 1:5, 1:6, and 1:8 were prepared in an attempt to increase the solubility and dissolution. Solubility, dissolution, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) of solid dispersions, physical mixtures (PM) and curcumin were evaluated. Both solubility and dissolution of curcumin solid dispersions were significantly greater than those observed for physical mixtures and intact curcumin. The powder X-ray diffractograms indicated that the amorphous curcumin was obtained from all solid dispersions. It was found that the optimum weight ratio for curcumin:PVP K-30 is 1:6. The 1:6 solid dispersion still in the amorphous from after storage at ambient temperature for 2 years and the dissolution profile did not significantly different from freshly prepared.

Growth and transport property measurements of rhenium doped tungsten diselenide single crystal

Single crystals of rhenium doped tungsten diselenide i.e. Re x W 1− x Se 2 ( x = 0, 0.0005, 0.001, 0.05, 0.1) are grown by vapour phase technique. The stoichiometry of grown single crystals is confirmed by energy dispersive analysis of X-rays. X-ray powder diffractograms obtained of these compounds were used for lattice parameter determination based on hexagonal system similar to that of host WSe 2.The crystallite size for each sample for different reflection is calculated using Scherrer's formula. Surface morphology as observed under optical microscope reflects that screw dislocation mechanism is responsible for growth of crystals. Electrical properties viz. Hall effect at room temperature, resistivity measurements at low temperature, and high pressure resistivity measurements indicates the semiconducting behaviour of Re x W 1− x Se 2 ( x = 0, 0.0005, 0.001, 0.05, 0.1) single crystals. Thermoelectric power measurements shows p-type nature of host WSe 2 whereas n-type nature of rhenium doped WSe 2 which matches with the results of Hall effect.

Intermolecular contacts influencing the conformational and geometric features of the pharmaceutically preferred mebendazole polymorph C

Mebendazole (MBZ) is a common benzimidazole anthelmintic that exists in three different polymorphic forms, A, B, and C. Polymorph C is the pharmaceutically preferred form due to its adequated aqueous solubility. No single crystal structure determinations depicting the nature of the crystal packing and molecular conformation and geometry have been performed on this compound. The crystal structure of mebendazole form C is resolved for the first time. Mebendazole form C crystallizes in the triclinic centrosymmetric space group and this drug is practically planar, since the least-squares methyl benzimidazolylcarbamate plane is much fitted on the forming atoms. However, the benzoyl group is twisted by 31(1) degrees from the benzimidazole ring, likewise the torsional angle between the benzene and carbonyl moieties is 27(1) degrees. The formerly described bends and other interesting intramolecular geometry features were viewed as consequence of the intermolecular contacts occurring within mebendazole C structure. Among these features, a conjugation decreasing through the imine nitrogen atom of the benzimidazole core and a further resonance path crossing the carbamate one were described. At last, the X-ray powder diffractogram of a form C rich mebendazole mixture was overlaid to the calculated one with the mebendazole crystal structure.

The Temperature-Dependent Structure of Alkylamines and Their Corresponding Alkylammonium-Alkylcarbamates

In spite of the wide use of alkylamine (AA) surfactants, little attention has been paid to their spontaneous reactivity in air. Exposure of AA surfactants to CO(2) results in the formation of alkylammonium-alkylcarbamate (AAAC) molecular pairs. The effect of hydrocarbon chain length on the reactivity of AAs was followed by monitoring mass gain vs time under atmospheric conditions as well as in a saturated CO(2) environment. The rates of conversion to AAAC decreased with hydrocarbon chain length. Indexed powder X-ray diffractograms and the corresponding unit cells are presented for all phases of AAs and AAACs with chain lengths of 14, 16, and 18 carbons. Temperature-resolved powder X-ray diffraction of AAACs indicated anisotropic thermal expansion occurring exclusively along the a direction of the unit cell.

A New Family of Bimetallic Framework Materials Showing Reversible Structural Transformations

Three new bimetallic framework compounds, namely, (([Cd 3(tn) 4][Co(CN) 6] 2) · 5H 2O) ∞ (1), ([Cd(tn)] 3[Cr(CN) 6] 2) ∞(2), and ([Cu 2(tn) 2][Ru(CN) 6] · 4H 2O) ∞ (3), have been prepared in a very simple manner from the ligand 1,3-diaminopropane (tn), the hexacyanometalates [Co(CN) 6] 3-, [Cr(CN) 6] 3- and [Ru(CN) 6] 4-, and a metal(II) sulfate (M IISO 4:M = Cd 2+, Cu 2+). They have been characterized by IR, X-ray diffraction, elemental analysis and immersion calorimetry. All three compounds have three-dimensional structures, with both the organic ligand and the cyanide groups acting as bridges. Compounds 1 and 3 have channels occupied by water molecules of crystallization. All three complexes are stable indefinitely when exposed to the air at room temperature; however, when compounds 1 and 3 are heated, they lose the water molecules of crystallization. The powder X-ray diffractograms of these dried and as yet unknown species are different from those of the original compounds. However, in a humid atmosphere both dried compounds readsorb water molecules and revert to the original structures, as shown by powder X-ray diffraction measurements. The adsorption properties of compounds 1 and 3 were studied using immersion calorimetry and in situ powder X-ray diffraction. In the case of compound 3 the heat of the structural transformation on rehydration was found to be ca. 19 ± J/g. © 2009 American Chemical Society.

Self-Assembly of Esters of Arjunolic Acid into Fibrous Networks and the Properties of their Organogels

Nine esters of a naturally occurring triterpenoid, arjunolic acid (from Terminalia arjuna), with alkyl chains have been synthesized, and their self-assembly has been studied in organic liquids. All of the esters examined were found to be excellent gelators. No birefringence was detected in optical micrographs of the transparent toluene gels with 5% (w/w) ethyl arjunolate or 5% (w/w) p-nitrobenzyl arjunolate as the gelator, but a spherulitic-type pattern was seen for a gel of 1.2% (w/w) p-nitrobenzyl arjunolate in 1/1 (w/w) chloroform/cyclohexane. Electron microscope images revealed self-assembled fibrillar network (SAFIN) structures with right-handed helical ribbons in some gels. With increasing concentration of the gelators, the gel-to-sol transition temperature (T(gel)) increased and then approached plateau values. Differential scanning thermograms demonstrated that the heats for transition from transparent gels to sols of ethyl arjunolate or p-nitrobenzyl ajunolate in toluene are very small. Powder X-ray diffractograms revealed that the molecular packing in the SAFIN of the 5% (w/w) ethyl aijunoate in the toluene gel was amorphous and similar to the diffractogram recorded for the neat gelator. Although the diffractogram of neat p-nitrobenzyl arjunolate consisted of broad peaks, suggesting disordered packing, the low-angle peaks of the corresponding toluene gel were much sharper; these results indicate more crystalline packing in the SAFIN than in the neat gelator. The kinetics and growth of the transformation of sols of p-nitrobenzyl arjunolate in 1/1 (w/w) chloroform/cyclohexane to their gels have been investigated at different incubation temperatures by circular dichroism spectroscopy. The data have been analyzed to probe the mechanism of SAFIN formation and the relationship between the molecular structures of the esters of arjunolic acid and their abilities to function as gelators of a wide variety of organic liquids.

Quantitative Evaluation of Minerals in Lignites and Intraseam Sediments from the Achlada Basin, Northern Greece

Seven core samples (five lignite samples and two intraseam nonlignite rock samples) from the Achlada open-cut mine in northern Greece were characterized by X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques. Quantitative evaluation of the mineral phases in each sample was made from the powder X-ray diffractograms using Siroquant commercial interpretation software, which is based on Rietveld principles. The main minerals in the low-temperature ash (LTA) ash of the lignites are kaolinite and illite, with bassanite and quartz in minor proportions. The nonlignite rock samples mainly consist of illite, mica (2M1), and kaolinite (poorly ordered), along with quartz, chlorite (ferroan), feldspar (albite), rutile, and dolomite. Oriented-aggregate XRD study further shows the presence of smectite, and interstratified illite/smectite (I/S), in the clay fractions of the lignite and rock samples, with the mineral matter of the lignites being richer in kaolinite, smectite, and I/S than in mineral matter of ...

Synthesis and characterization of nickel(II), cobalt(II), manganese(II), copper(II), iron(III) and chromium(III) complexes of unsymmetrical salen-type ligand and their application as catalysts for the oxidation of styrene

Salen type ligand has been synthesized in high yield, from which the nickel(II), cobalt(II), manganese(II), copper(II), iron(III) and chromium(III) complexes have been synthesized. The resulting complexes have been characterized by elemental analyses, IR and electronic spectral data, magnetic susceptibility measurements and thermogravimetric analysis. The complexes have been tested for their ability to activate molecular oxygen in the catalytic oxidation of styrene. Manganese(II), nickel(II) and chrornium(III) complexes show slight high catalytic activity towards oxidation of styrene as compared to others. Scanning electron micrograph and powder X-ray diffractogram have also been reported.

Growth and characterization of pure and doped bis thiourea zinc acetate: Semiorganic nonlinear optical single crystals

Metal–organic coordination complex single crystals bis thiourea zinc acetate (BTZA) and Cd2+ doped BTZA have been synthesized and grown successfully by slow-cooling technique from their aqueous solutions. Single crystals of pure and Cd2+ doped BTZA with dimensions of 35×4×2mm3 and 10×5×6mm3, respectively were obtained with well defined morphology. The as grown single crystals are characterized by single crystal XRD studies and melting point measurements which reveal the incorporation of metallic dopants has not changed the structure of the parent crystal. The powder X-ray diffractogram of the grown crystals has been recorded and the various planes of reflection identified shows shift in the peak positions. The metal coordination with thiourea through sulphur in pure and Cd2+ doped BTZA were ascertained by FTIR studies and optical absorption study to identify the UV cut-off range. The presence of metals in pure and Cd2+ doped BTZA crystal lattice were confirmed by atomic absorption spectroscopy (AAS). The thermal decomposition of pure and Cd2+ doped BTZA crystals were investigated by thermo gravimetric analyses (TGA) and differential thermal analysis (DTA) indicate that doped crystals are more stable than pure crystals. The dielectric response of the crystals were studied in the frequency range 100Hz–5MHz at different temperatures and the results are discussed. Second harmonic generation (SHG) measurement confirms that the pure and Cd2+ doped BTZA have nonlinear optical (NLO) property. Laser damage threshold value of 12.44MW/cm2 has been determined using Q-switched Nd:YAG laser operating at 1064nm and with 8ns pulses in single shot mode for pure BTZA single crystal is reported for the first time.

Structural transitions in amorphousH2O and D2O: the effect of temperature

We have recently observed amorphous–amorphous transitions incurred upondecompressing very high density amorphous ice (VHDA) at 140 K from 1.1 to<0.02 GPa in a piston–cylinder setup by monitoring the piston displacement as a function ofpressure and by taking powder x-ray diffractograms of quench-recovered samples(Winkel et al 2008 J. Chem. Phys. 128 044510). Here we study the effect ofchanging the temperature from 77 to 160 K during decompression from 1.1 to<0.02 GPa, and the effectof substituting D2O for H2O at 140 and 143 K. At 77 K all structural transitions are arrested and six-coordinated VHDAis quench recovered. At 125–136 K the continuous transition to five-coordinated expandedhigh density amorphous ice (eHDA) takes place. At 139–140 K, both the continuoustransition to eHDA and the quasi-discontinuous transition to four-coordinated LDA areobserved, i.e. . At 142–144 K, crystallization to mixtures of cubic ice Ic and ice IX is observed prior tothe quasi-discontinuous transition, i.e. Ic/ice IX. At 160 K ice Ic is recovered, which most likely transforms from a high-pressureice (HPI) such as ice V, i.e. Ic. Exchanging D2O for H2O at 140 K does not significantly affect the amorphous–amorphous transitions:both the decompression curves and the powder x-ray diffractogramsare unaffected within the experimental resolution. However, at 143 KD2O–VHDA can be decompressed according to the sequence , i.e. crystallization can be suppressed at∼3 K higher temperatures.