The University of Nevada, Las Vegas (UNLV) High Pressure Science and Engineering Center is supported by Department of Energy-National Nuclear Security Administration (NNSA) Cooperative Agreement DE-NA0001982. This work was performed at the High Pressure Collaborative Access Team (HPCAT) (Sector 16), and at the GeoSoilEnviroCARS (GSECARS) (Sector 13), Advanced Photon Source (APS), Argonne National Laboratory (ANL). HPCAT operations are supported by DOE-NNSA under Award No. DE-NA0001974 and DOE-BES under Award No. DE-FG02-99ER45775, with partial instrumentation funding by NSF. GeoSoilEnviroCARS is supported by the National Science Foundation&#8212;Earth Sciences (EAR-0622171) and Department of Energy (DOE)&#8211;Geosciences (DE-FG02-94ER14466). APS is supported by DOE-BES, under Contract DE-AC02-06CH11357. We thank GSECARS and COMPRES for the use of the Gas Loading System.

1. Diamond Anvil Cell and Gasket Preparation
<ol>
	<li>Select a pair of diamond anvils with conical design12 and matching culet size. The conical anvil design is chosen for the wide angular x-ray windows it provides, allowing to collect relatively high resolution x-ray microdiffraction data. The culet (flat or beveled tip of a diamond anvil) is selected according to the maximum target pressure. The diameter of the flat part of the culet ranges from about 1-0.07 mm for target pressures from 10 to more than 20...

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K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Double-sided+laser+heating+system+at+HPCAT+for+in+situ+x-ray+diffraction+at+high+pressures+and+high+temperatures.">Double-sided laser heating system at HPCAT for in situ x-ray diffraction at high pressures and high temperatures.</a> J. Phys.-Cond. Mat. 18, 1097-1103 (2006).</li><li>Prakapenka, V. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advanced+flat+top+laser+heating+system+for+high+pressure+research+at+GSECARS:+application+to+the+melting+behavior+of+germanium.">Advanced flat top laser heating system for high pressure research at GSECARS: application to the melting behavior of germanium.</a> High Press. 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Phys. 46, 2774-2780 (1975).</li><li>Mao, H., Bell, P., Shaener, J., Steinberg, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Specific+volume+measurements+of+Cu,+Mo,+Pd,+and+Ag+and+calibration+of+ruby+R1+fluorescence+pressure+gauge+from+0.06+to+1+Mbar.">Specific volume measurements of Cu, Mo, Pd, and Ag and calibration of ruby R1 fluorescence pressure gauge from 0.06 to 1 Mbar.</a> J. Appl. Phys. 49, 3276-3283 (1978).</li><li>Dorfman, S. M., Prakapenka, V. B., Meng, Y., Duffy, T. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=+Intercomparison+of+pressure+standards+(Au,+Pt,+Mo,+MgO,+NaCl+and+Ne)+to+2.5+Mbar."> Intercomparison of pressure standards (Au, Pt, Mo, MgO, NaCl and Ne) to 2.5 Mbar.</a> J. Geophys. 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T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+pressure+single-crystal+micro+X-ray+diffraction+analysis+with+GSE_ADA/RSV+software.">High pressure single-crystal micro X-ray diffraction analysis with GSE_ADA/RSV software.</a> High Pressure Research. 33, 466-484 (2013).</li><li>Grunbaum, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Remark+on+phase+problem+in+crystallography.">Remark on phase problem in crystallography.</a> Proc. Natl. Acad. Sci. U.S.A. 72, 1699-1701 (1975).</li><li>Hauptman, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+phase+problem+of+x-ray+crystallography.">The phase problem of x-ray crystallography.</a> Rep. Progr. 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The authors declare no conflict of interest.

Every step of the described protocol must be performed with great care to avoid risks of experimental failure via catastrophic shatter of the anvils, gasket instability and loss of pressure, inability to achieve target temperature, sample contaminations, severe non-hydrostaticity, etc.
The greatest challenge of high P-T synthesis is the interpretation of x-ray diffraction data, a problem too extensive to be summarized here. While structural solution is inherently a non-trivial problem...

Pressure can fundamentally change the properties and bonding of matter. The Earth&#39;s topography, composition, dynamics, magnetism and even the atmosphere composition are profoundly tied to processes occurring at the interior of the planet which is under extremely high pressure and temperature. Deep Earth processes include earthquakes, volcanism, thermal and chemical convection, and differentiation. High pressure and temperature are used to synthesize super-hard materials like diamond and cubic boron nitride. High PT synthesis combined with in situ x-ray diffraction allows researchers to identify the crystal structures of the new materials or high-pressure polymorphs of extreme technological importance. The knowledge of high-pressure structures and properties allows interpretation of the structure and processes of planetary interiors, modeling of the performance of materials under extreme conditions, synthesis and design of new materials, and achievement of a broader fundamental understanding of materials&#39; behavior. The exploration of high pressure phases is technically demanding due to the twofold challenges of controllably generating extreme environmental conditions and probing small samples within bulky environmental cells.
A range of materials and techniques may be used to perform synthesis at extreme conditions2, 3. The most suitable equipment for each particular experiment depends on the material investigated, the target PT, and the probing techniques. Among high pressure devices, the LH-DAC has smallest sample size, but is however capable of reaching the highest static PT (above 5 Mbar and 6,000 K) and allows the highest resolution x-ray structural analysis. The protocol described below led to the discovery of Fe4O5 1 and is applicable to a wide range of materials and synthesis conditions. The LH-DAC is best suited for materials efficiently absorbing the laser wavelength of ~1 &#181;m available at high pressure synchrotron beamlines (e.g. 16-IDB and 13-IDD stations at the Advanced Photon Source, Argonne National Lab), for synthesis pressures up to 5 Mbar and for temperatures greater than about 1,500 K. Fairly complex structures and multiphase samples can be characterized with the x-ray microdiffraction strategies presented here. Other techniques, such as whole DAC heating4 and local resistive heating, are suitable for lower synthesis temperatures. CO2 5 laser heating, with wavelength of about 10 &#181;m, is suitable for the heating of materials transparent to the infrared YLF laser but absorbing the CO2 radiation. Other devices, such as multi-anvil, piston-cylinder and Paris-Edinburgh presses, provide larger volume samples necessary for neutron diffraction experiments, for instance.
In the LH-DAC, invented in 19676, 7, 8, high pressure is generated on a small sample placed between the tips of two opposed diamond anvils. In the laser heating systems installed at synchrotron experimental stations9, 10, 11, laser beams are delivered on a sample from both sides through the diamond anvils while a brilliant x-ray beam is focused on the heated spot. Samples absorbing the laser light are heated while x-ray diffraction is used to monitor the progress of the synthesis. The thermal radiation emitted by the laser heated sample is temperature dependent. Thermal emission spectra collected from both sides of the sample are used to calculate the sample temperature by fitting the spectra to the Plank radiation function assuming black body behavior8.
The crystal structure analysis of products of synthesis in a LH-DAC is carried out using the brilliant synchrotron x-ray beam, high precision motorized stages and the fast x-ray detectors available at dedicated synchrotron experimental stations. We collect x-ray diffraction data in a 2D grid and customize the data collection strategy according to the grain size. This approach allows to: i) map the sample composition; ii) obtain robust data analysis of a complex multiphase sample by combining single crystal, powder and multi-grain diffraction techniques.

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		<tr height="21">
			<td height="21" style="height:21px;width:195px;">diamond anvils</td>
			<td style="width:119px;">Almax Easylab</td>
			<td style="width:136px;">N/A</td>
			<td style="width:119px;"></td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:195px;">WC seats</td>
			<td style="width:119px;">Almax Easylab</td>
			<td style="width:136px;">N/A</td>
			<td style="width:119px;">The conical housing needs to match the conical shape of the anvil bottom</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">SX-165 CCD</td>
			<td style="width:119px;">Marresearch</td>
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		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">XRD 1621 xN ES</td>
			<td style="width:119px;">Perkin Elmer</td>
			<td style="width:136px;"></td>
			<td style="width:119px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">W needle</td>
			<td style="width:119px;">Ted pella, Inc</td>
			<td style="width:136px;">MT26020</td>
			<td style="width:119px;"></td>
		</tr>
	</tbody>
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synthesis and microdiffraction at extreme pressures and temperatures

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary interiors, design materials with novel properties, understand the mechanical behavior of materials exposed to very high stresses as in explosions or impacts. Synthesis and structural analysis of materials at extreme conditions of pressure and temperature entails remarkable technical challenges. In the laser heated diamond anvil cell (LH-DAC), very high pressure is generated between the tips of two opposing diamond anvils forced against each other; focused infrared laser beams, shined through the diamonds, allow to reach very high temperatures on samples absorbing the laser radiation. When the LH-DAC is installed in a synchrotron beamline that provides extremely brilliant x-ray radiation, the structure of materials under extreme conditions can be probed in situ. LH-DAC samples, although very small, can show highly variable grain size, phase and chemical composition. In order to obtain the high resolution structural analysis and the most comprehensive characterization of a sample, we collect diffraction data in 2D grids and combine powder, single crystal and multigrain diffraction techniques. Representative results obtained in the synthesis of a new iron oxide, Fe4O5 1 will be shown.

We show representative microdiffraction data obtained from the high pressure and temperature synthesis of Fe4O5 from a mixture of hematite and iron according to the reaction:
<img src="/files/ftp_upload/50613/50613eq1.jpg" alt="Equation 1" width="450px" fo:content-width="4in" />
Figure 5 illustrates powder diffraction patterns from B locations. Although they were collected a few microns apart, the patterns are remarkably differ...

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Synthesis and Microdiffraction at Extreme Pressures and Temperatures

The laser heated diamond anvil cell combined with synchrotron micro-diffraction techniques allows researchers to explore the nature and properties of new phases of matter at extreme pressure and temperature (PT) conditions. Heterogeneous samples can be characterized in situ under high pressure by 2D mapping and combined powder, single-crystal and multigrain diffraction approaches.

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary ...

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11.1K vistas.  University of Nevada, Las Vegas. La calefacción celda de yunque de diamante láser combinado con técnicas de micro-difracción sincrotrón permite a los investigadores a explorar la naturaleza y propiedades de las nuevas fases de la materia a la presión y la temperatura (PT) condiciones extremas. Muestras heterogéneas pueden caracterizarse In situ A alta presión mediante cartografía 2D y en polvo combinada, de un solo cristal y métodos de difracción multigrano.