Merrill-Bassett Diamond Anvil Cell Research Articles

Use of a miniature diamond-anvil cell in a joint X-ray and neutron high-pressure study on copper sulfate pentahydrate.

Single-crystal X-ray and neutron diffraction data are usually collected using separate samples. This is a disadvantage when the sample is studied at high pressure because it is very difficult to achieve exactly the same pressure in two separate experiments, especially if the neutron data are collected using Laue methods where precise absolute values of the unit-cell dimensions cannot be measured to check how close the pressures are. In this study, diffraction data have been collected under the same conditions on the same sample of copper(II) sulfate pentahydrate, using a conventional laboratory diffractometer and source for the X-ray measurements and the Koala single-crystal Laue diffractometer at the ANSTO facility for the neutron measurements. The sample, of dimensions 0.40 × 0.22 × 0.20 mm3 and held at a pressure of 0.71 GPa, was contained in a miniature Merrill-Bassett diamond-anvil cell. The highly penetrating diffracted neutron beams passing through the metal body of the miniature cell as well as through the diamonds yielded data suitable for structure refinement, and compensated for the low completeness of the X-ray measurements, which was only 24% on account of the triclinic symmetry of the sample and the shading of reciprocal space by the cell. The two data-sets were combined in a single 'XN' structure refinement in which all atoms, including H atoms, were refined with anisotropic displacement parameters. The precision of the structural parameters was improved by a factor of up to 50% in the XN refinement compared with refinements using the X-ray or neutron data separately.

Hingeless negative linear compression in the mechanochromic gold complex [(C6F5Au)2(μ-1,4-diisocyanobenzene)

The compression of a crystalline material under hydrostatic pressure always results in a reduction in volume of the solid, with the observed reduction typically occurring in all crystallographic cell parameters.1 However, there are a number of exceptional materials that have been shown to expand in a specific direction upon hydrostatic compression while maintaining a positive volume compression. The phenomenon of uni-or biaxial expansion under compression is known as negative linear compressibility (NLC).1 Rare examples of NLC have attracted attention recently owing to the potential applications in a range of materials, including body armor, artificial muscle actuators, and pressure sensors.2

Phase transitions and isothermal equations of state of epsilon hexanitrohexaazaisowurtzitane (CL-20)

The phase stability of epsilon hexanitrohexaazaisowurtzitane at high pressure and temperature was investigated using synchrotron angle-dispersive x-ray diffraction experiments. The samples were compressed at room temperature using a Merrill–Bassett diamond anvil cell. For high-temperature compression experiments a hydrothermal diamond anvil cell developed by Bassett was used. Pressures and temperatures of around 5 GPa and 175 °C, respectively, were achieved. The epsilon phase was determined to be stable under ambient pressure to a temperature of 120 °C. A phase transition to the gamma phase was seen at 125 °C and the gamma phase remained stable until thermal decomposition above 150 °C. Pressure-volume data for the epsilon phase at ambient and 75 °C were fitted to the Birch–Murnaghan formalism to obtain isothermal equations of state.

Incorporation of a new design of backing seat and anvil in a Merrill–Bassett diamond anvil cell

A modification to the Merrill–Bassett miniature diamond anvil cell is reported here, with the inclusion of tungsten carbide backing seats with Boehler–Almax-cut diamonds to replace the previously used beryllium seats and (typically) modified brilliant-cut anvils. This has led to the removal of troublesome beryllium powder lines from diffraction images, while maintaining the pressure range and opening angle of the original design.

Halogen...halogen interactions in pressure-frozen ortho- and meta-dichlorobenzene isomers

Isomers 1,2-dichlorobenzene (o-DCB) and 1,3-dichlorobenzene (m-DCB) were high-pressure frozen in-situ in a Merrill-Bassett diamond-anvil cell and their structures determined at room temperature and at 0.18 (5) GPa for o-DCB, and 0.17 (5) GPa for m-DCB by single-crystal X-ray diffraction. The patterns of halogen...halogen intermolecular interactions in these structures can be considered to be the main cohesive forces responsible for the molecular arrangements in these crystals. The molecular packing of dichlorobenzene isomers, including three polymorphs of 1,4-dichlorobenzene (p-DCB), have been compared and relations between their molecular symmetry, packing arrangements, intermolecular interactions and melting points discussed. The topology of the crystal packing in dichlorobenzene isomers results from the interplay of the molecular shape, steric hindrances and intermolecular interactions. The non-planar arrangement of the dichlorobenzene molecules in the crystal structures can be justified by the distributions of the electrostatic potential on molecular surfaces, which determines electrostatic intermolecular interactions.

Effect of pressure up to 5.5 GPa on dry powder samples of chlorpropamide form-A

The effect of pressure up to 5.5 GPa on a dry powder sample of chlorpropamide (4-chloro- N-((propylamino)-carbonyl)-benzenesulfonamide), form-A (sp. gr. P2 12 12 1, a = 9.066 Å, b = 5.218 Å, c = 26.604 Å), was studied in situ in a Merrill–Bassett diamond anvil cell using high-resolution X-ray powder diffraction (a synchrotron radiation source at SNBL ESRF, Grenoble). No evidence of the polymorphic transformation of chlorpropamide form-A to form-C was observed. The A–C polymorphic transition on tabletting previously reported by Otsuka et al. (1989) is therefore likely to be due to local heating effects. Similarly, the phase transitions of form-A reported by Cao (2002) to be induced by pressure applied to a sample in its saturated ethanol solution (at 0.9 and at 2.0 GPa) would appear to be solvent-mediated. In the dry sample, a phase transition may be supposed to occur at pressures above 4 GPa, but this requires further studies.

Realizing Predicted Crystal Structures at Extreme Conditions: The Low-Temperature and High-Pressure Crystal Structures of 2-Chlorophenol and 4-Fluorophenol

A crystal of 2-chlorophenol was grown from the liquid at ambient pressure by laser-assisted zone refinement; 4-fluorophenol was crystallized from ethanol. Different polymorphs were obtained at high pressure by compression of the liquids in a Merrill-Bassett diamond-anvil cell (crystallization pressures 0.12 and 0.28 GPa, respectively). The structures of all phases are characterized by OH···OH hydrogen-bond formation. In the ambient-pressure polymorph of 2-chlorophenol, a hydrogen-bonded chain is formed about a 32 screw-axis; the ambient-pressure phase of 4-fluorophenol contains hexameric rings located on 3̄ sites. In crystallizing in high-symmetry space groups, these two compounds conform to typical behavior for bulky monoalcohols. By contrast, at high-pressure both compounds form zigzag chains disposed about 21 screw-axes, behavior more characteristic of small monoalcohols. The halophenol moiety thus behaves as a bulky group at ambient pressure but a small group at high pressure. We show that Crystal Structure Prediction methodologies reproduce all four phases, even though the potentials used were developed using ambient-pressure data. This is especially encouraging as the ambient-pressure phase of 2-chlorophenol contains three molecules in the asymmetric unit, while the high-pressure phase of 4-fluorophenol is disordered.

In-situ pressure crystallization and X-ray diffraction study of 1,1,2,2-tetrachloroethane at 0.5 GPa

Abstract 1,1,2,2-Tetrachloroethane, C2H2Cl4 (denoted TCE, m.p. 230 K) has been in-situ pressure crystallized in a Merrill-Bassett diamond-anvil cell, and its structure has been determined at 0.5 GPa and 295 K from the single-crystal X-ray diffraction data. TCE crystallizes in the monoclinic space group P21 /c with the molecules located at the inversion centers. The molecules are in the s-trans conformation, while they assume the gauche conformation in the crystal obtained by cooling. This implies that a phase transition may exist between the low-temperature and high-pressure phases of TCE. In the high-pressure phase the HC–CH moiety of the C2H2Cl4 molecule is disordered in two sites, one related to the other by the non-crystallographic mirror plane approximately through the four Cl atoms of one molecule. The refined occupancy factors for the disordered sites are 0.77 and 0.23. The role played by the Cl…Cl intermolecular interactions for the disorder, and the phase transition between TCE phases built of s-trans (high-pressure) and gauche (low-temperature) molecules have been discussed.

High-pressurein-situcrystallization, structure and phase transitions in 1,2-dichloroethane

AbstractThe single crystal of 1,2-dichloroethane, C2H4Cl2wasin-situcrystallized in a Merrill-Bassett diamond-anvil cell, and its structure determined at 0.7 GPa and 280 K. The crystals are monoclinic, space groupP21/c. The C2H4Cl2molecules in thes-transconformation are located at the inversion centers. The —H2C—CH2—ethylene group is disordered in two sites, with equal occupancies, one rotated by 180° to the other about the Cl⋯Cl axis of the molecule. The crystal cohesion forces have been attributed mainly to Cl⋯Cl intermolecular interactions, and their role in the mechanism of the phase transition at 177 K has been analysed. It was found that the order-disorder phase transition in the structure of 1,2-dichloroethane is associated with the breaking of the Cl⋯Cl intermolecular interactions in the disordered phase. The crystal amorphization under non-homogeneous strain and subsequent transition to a new pressure-induced polymorph at 1.5 GPa has been observed.

New insights on high-pressure behaviour of microporous materials from X-ray single-crystal data

The main deformation mechanisms induced by pressure on different structural types of zeolites were analysed by comparing experimental data and theoretical models. Data of single-crystal X-ray diffraction obtained with the sample in a Merrill–Bassett diamond anvil cell on a four-circle diffractometer were collected at different pressures for samples of heulandite, scolecite and bikitaite, using non-penetrating pressure transmitting media (glycerol or silicon oil), up to 5 GPa. The results indicated that, at first approximation, the theoretical approach reproduces the structural evolution of zeolites under pressure. However, the flexibility possessed by framework microporous silicates resulted more complex than that which can be modelled by undeformable “rigid-unit modes”, being completely flexible in the oxygen hinges. Moreover, the compressibility of the zeolites under study does not appear to be directly related to the microporosity represented by the framework density (FD): the bulk moduli (simply defined as the inverse of volume compressibility coefficients) of heulandite (27.5(2) GPa) and scolecite (54.6(3) GPa) were different even though their FD’s were quite similar. Single crystal data have shown that the structural evolution of the open-framework silicates, is strongly controlled by the framework, whereas the role of the extra-framework content was less important. In all three zeolites the position of the extra-framework water molecules and cations was maintained approximately and their coordination numbers remained unchanged within the pressure range investigated.

Effects of pressure on the structure of bikitaite

The structural behaviour of bikitaite, Li 2 (Al 2 Si 4 O 12 ). 2H 2 O, was investigated under hydrostatic pressure using X-ray single-crystal diffraction data. A Merrill-Bassett diamond anvil cell was mounted with glycerol, as non penetrating pressure-transmitting medium, ruby chips and a small crystal of quartz as the calibrant. A strong anisotropic compression was observed by linear regressions of lattice parameters against P, bikitaite being softer along the c axis (βc = 9.3(1) 10 -3 GPa -1 ), than along b (β b = 6.6(1) 10 -3 GPa -1 ) and a (β a = 2.4(1) 10 -3 GPa -1 ) (β a : β b : β c = 1 : 2.75 : 3.9). Fitting the cell-volume — pressure data to a second order Birch-Murnaghan equation of state, as indicated by the finite strain-stress plot, yielded K 0 = 44.2(4) GPa, with K’ = 4 and V 0 = 295.58(2) A 3 . The evolution of the bikitaite structure with P was studied by comparing the results of refinements with data collected at room conditions, at 3.2 GPa and after decompression. The structure can be described as sheets of six-membered rings parallel to (001), connected by pyroxene-like chains. 8-ring and 5-ring channels run along [0 10] and inside the 8-ring channel there is a onedimensional chain of water molecules, which is linked to the framework through the extra-framework Li atoms. Under pressure, the kinking of the pyroxene-like chain decreased the free diameters of the 5-ring channels, strongly reducing the distance between the ab planes. On the contrary, the tridymite-like planes with 6-membered rings were more rigid. The positions of the extra-framework cations and water were maintained at HP even though the configuration of the water chains changed slightly: the distances between the water molecules decreased, whereas the kinking angle of the chain increased.

High-pressure single-crystal X-ray diffraction study of katoite hydrogarnet: Evidence for a phase transition fromIa3d→I4̅3dsymmetry at 5 GPa

The crystal structure of katoite hydrogarnet has been refined at 0.0001, 2.15, 4.21, 5.09, 6.00, 7.09, and 7.78 GPa from single-crystal X-ray diffraction data using a 4:1 methanol:ethanol mixture as pressure medium in a Merrill-Bassett diamond-anvil cell. Below ~5 GPa, the katoite structure has Ia3d symmetry and compresses by bond shortening rather than bond bending, in agreement with recent quantum mechanical calculations. An unconstrained third-order Birch-Murnaghan fit to the unit-cell volumes and pressures for Ia3d symmetry gave the following equation of state parameters: Vo = 1987.6(1) Å3, Ko = 58(1) GPa and K' = 4.0(7). Above this pressure, the structure undergoes a phase transition to space group I4̅3d, a non-centric subgroup of Ia3d. In the I4̅3d structure, there are two non-equivalent (O4H4) groups. Both the Ca and Al atoms are displaced along a relative to their positions in Ia3d. It is proposed that compression of the short H-H distance between (O4H4) groups destabilizes the structure and may initiate the observed phase transition. Corroboration of this model will require accurate information on the hydrogen atom positions at pressures above 5 GPa.

Electronic and Structural High Pressure Properties of CuGaS 2 Chalcopyrite Semiconductor

We have investigated high-pressure structural properties and ab-initio band structure calculations of the ternary CuGaS 2 by single crystal X-ray diffraction up to 8 GPa. The single crystal X-ray diffraction experiments were performed in a Merrill-Bassett diamond anvil cell. The analysis of the X-ray data makes possible the accurate determination of the atomic position of the unit cell under pressure. The structural parameter u and the Cu-S and Ga-S bond lengths have been deduced. The results of the electronics band structure calculation using a first-principles pseudo-potential method and the local density approximation (LDA) are reported. The pressure derivatives of the energy gap are calculated and the values are in reasonable good agreement with the experimental ones.

Anisotropic crystal structure distortion of the monoclinic polymorph of acetaminophen at high hydrostatic pressures.

The anisotropy of structural distortion of the monoclinic polymorph of acetaminophen induced by hydrostatic pressure up to 4.0 GPa was studied by single-crystal X-ray diffraction in a Merrill-Bassett diamond anvil cell (DAC). The space group (P2(1)/n) and the general structural pattern remained unchanged with pressure. Despite the overall decrease in the molar volume with pressure, the structure expanded in particular crystallographic directions. One of the linear cell parameters (c) passed through a minimum as the pressure increased. The intramolecular bond lengths changed only slightly with pressure, but the changes in the dihedral and torsion angles were very large. The compressibility of the intermolecular hydrogen bonds NH...O and OH...O was measured. NH...O bonds were shown to be slightly more compressible than OH...O bonds. The anisotropy of structural distortion was analysed in detail in relation to the pressure-induced changes in the molecular conformations, to the compression of the hydrogen-bond network, and to the changes in the orientation of molecules with respect to each other in the pleated sheets in the structure. Dirichlet domains were calculated in order to analyse the relative shifts of the centroids of the hydrogen-bonded cycles and of the centroids of the benzene rings with pressure.

Pressure dependence of structural parameters of paragonite

The compressibility and structure of a 2M1 paragonite with composition [Na0.88K0.10Ca0.01Ba0.01] [Al1.97Ti0.007Fe0.01Mn0.002Mg0.006]Si3.01Al0.99O10OH2 were determined at pressures between 1 bar and 41 kbar, by single crystal X-ray diffraction using a Merrill-Bassett diamond anvil cell. Compressibility turned out to be largely anisotropic, linear compressibility coefficients parallel to the unit cell edges being βa=3.5(1)·10−4, βb=3.6(1)·10−4, βc=8.3(3)·10−4 kbar−1 (βa:βb·βc=1:1028:2.371). The isothermal bulk modulus, calculated as the reciprocal of the mean compressibility of the cell volume, was 650(20) kbar. The main features of the deformation mechanism resulting from structural refinements at pressures of 0.5, 25.4, 40.5 kbar were: – variation in sheet thickness, showing that compression of the c parameter was mainly due to the interlayer thickness reduction from 3.07 A at 0.5 kbar to 2.81 A at 40.5 kbar; – the compressibility of octahedra was greater than that of tetrahedra, the dimensional misfit between tetrahedral and octahedral sheets increased with P, so that tetrahedral rotation angel α increased from 15° at 0.5 kbar to 21.6° at 40.5 kbar; – the basal surface corrugation (Δz) of the tetrahedral layer, due to the different dimensions of M1 and M2 octahedra and to the octahedral distortion, decreased with P (Δz=0.19 and 0.12 A at 0.5 and 40.5 kbar respectively). Comparison of the new data on paragonite with those of a K-muscovite and a Na-rich muscovite (Comodi and Zanazzi 1995) revealed a clear trend toward decreasing of compressibility when Na substitutes for K atoms in the interlayer sites.

Compressibility of lysozyme protein crystals by X-ray diffraction.

Single-crystal high-pressure X-ray diffraction studies on the protein crystals of orthorhombic and tetragonal hen egg-white lysozyme polymorphs were carried out using a Merrill-Bassett diamond-anvil cell, image-plate detector and synchrotron radiation. The orthorhombic crystal has been squeezed to 85.5% of its ambient pressure volume at about 1.0 GPa; the crystal compresses anisotropically, and neither a glass transition or denaturation was observed. The tetragonal polymorph of lysozyme undergoes amorphization at pressures about 0.2 GPa.

High-pressure structural study of muscovite

The compressibility and structural variations of two 2M1 muscovites having compositions (Na0.07K0.90 Ba0.01□0.02)(Al1.84Ti0.04Fe0.07Mg0.04)(Si3.02Al0.98) O10 (OH)2 (7 mole % paragonite) and (Na0.37K0.60□0.03)(Al1.84Ti0.02 Fe0.10Mg0.06)(Si3.03Al0.97) O10(OH)2 (37 mole % paragonite) were determined at pressures between 1 bar and 35 kbar, by single-crystal X-ray diffraction using a Merrill-Bassett diamond anvil cell. Isothermal bulk moduli, setting K′ = 4, were 490 and 540 (± 30) kbar for the Na-poor and Na-rich samples respectively. Both samples show highly anisotropic compressibility patterns, with β a ∶β b ∶β c = 1∶1.15∶3.95 for the Na-poor sample and β a ∶β b ∶β c = 1∶1.19∶3.46 for the Na-rich one. HP structural refinements showed that the different compressibility was largely due to the partial substitution of Na for K in the interlayer region. Moreover, the different compressibility of the tetrahedral and octahedral layers, observed in both micas, increased the a rotation of the tetrahedral layer by about 2° in 28 kbar, as also indicated by the evolution of interlayer cation bond lengths. This increases the repulsion of oxygens of the basal layers and between the high-charged cations of the tetrahedral layer. As a consequence, phengitic substitution, reducing α rotation, would increase the baric stability of mica. Comparison between the HP structures of muscovite and phlogopite indicated the lower compressibility of the latter, mainly due to the greater compressibility of the dioctahedral layer with respect to that of the trioctahedral layer. The HT and HP behaviour of di- and trioctahedral micas showed an anisotropy in the compressional pattern which was markedly greater than that observed in the dilatation pattern. This unexpected result was explained by the different evolution with P and T of alkaliO bond lengths. By combining HP and HT data, a tentative equation of state of muscovite is proposed.

Multichannel Raman spectrometry system for weakly scattering materials at simultaneous high pressures and high temperatures

A Raman system is described which is suitable for rapid determination of Raman spectra of silicates and other weak Raman scatterers under simultaneous high-pressure and high- temperature conditions. Samples are pressurized with an argon pressure medium and Sm:YAG pressure standard in an Inconel 718 or rhenium Merrill–Bassett diamond–anvil cell that is externally heated in a vacuum oven equipped with quartz windows on either side. Raman spectra are excited and collected through the front window using ≊160° scattering geometry. A triple spectrometer in conjunction with a holographic notch filter, disperses the Raman scattered radiation onto a liquid-nitrogen-cooled CCD detector. Simultaneously measured Sm:YAG fluorescence spectra are collected through the rear window and routed via an optical fiber to a second multichannel spectrometer system equipped with a diode-array detector. The high sensitivity of the detectors and the simultaneous measurement technique enable detection of and compensation of pressure drifts occurring at high temperature. The performance of the system is demonstrated by measurement of the positions and linewidths of the high-frequency Raman modes of polycrystalline forsterite (α-Mg2SiO4) at temperatures up to 930 K at pressures of ∼8 GPa and up to 842 K at pressures in the range 12–14 GPa.

New chemical reactions in methane at high temperatures and pressures

The authors have used a Merrill-Bassett diamond anvil cell and Raman spectroscopy to study methane at high pressures (up to 13 GPa) and high temperatures (up to 912 K). At 2.5-5.0 GPa and 912 K, methane photoreacts with the laser light used for Raman spectroscopy and forms a graphitelike soot compound. At room temperature and pressure the Raman spectrum of the new material has an intense peak with a frequency of 1597 cm[sup [minus]1]. At higher pressures and temperatures (10-13 GPa and 948 K) a sample of [sup 13]CD[sub 4] methane photoreacted with the laser light and formed a hard, clear, solid film. At 0.34 GPa and 300 K, this film had Raman peaks at 541 and 1605 cm[sup [minus]1]. The 541-cm[sup [minus]1] peak may correspond to the 550-cm[sup [minus]1] peak found in some diamondlike carbon (DLC) films formed by chemical vapor deposition (CVD), but the 1605-cm[sup [minus]1] peak does not appear to have any such counterpart. Other possible Raman peaks were masked by interference from the diamond anvils. Thus, while the hard, clear film has some similarities to CVD DLC films, some important differences and questions remain. 35 refs., 5 figs.

The comparative compressibility of reedmergnerite, danburite and their aluminium analogues

The compressibilities of reedmergnerite (NaBSi 3 O 8 ) and danburite (CaB 2 Si 2 O 8 ) have been determined between 0 GPa and 5 GPa by single crystal X-ray diffraction, using a Merrill-Bassett diamond anvil cell. Further compressibility studies on anorthite (CaAl 2 Si 2 O 8 ) between 0 GPa and 2.55 GPa and the use of previously published data for albite (NaAlSi 3 O 8 ) enabled the Murnaghan equation of state to be fitted to the volume, pressure data and a bulk modulus obtained for each crystal structure. For a straight comparison of unit cell volume changes with pressure it was necessary to fix K' at 4. For sections involving the change of bulk modulus with increasing Al/Si disorder K' was fixed at four separate values to confirm that the trends observed were real. Comparison of changes in unit cell volume with pressure allows a number of conclusions to be made : The extra framework cation M″ plays a major role in determining structure compressibility, substitution of B for Al results in a increase in bulk modulus, and increasing Al/Si disorder leads to a decrease in the bulk modulus of the anorthite structure. The comparison of strain ellipsoids for reedmergnerite and albite confirm that the major structural changes with increasing pressure are driven by changes in T-O-T bond angles