Melting line of calcium characterized by in situ LH-DAC XRD and first-principles calculations

AbstractIn this work, the melting line of calcium has been characterized both experimentally, using synchrotron X-ray diffraction in laser-heated diamond-anvil cells, and theoretically, using first-principles calculations. In the investigated pressure and temperature range (pressure between 10 and 40 GPa and temperature between 300 and 3000 K) it was possible to observe the face-centred phase of calcium and to confirm (and characterize for the first time at these conditions) the presence of the body-centred cubic and the simple cubic phase of calcium. The melting points obtained with the two techniques are in excellent agreement. Furthermore, the present results agree with the only existing melting line of calcium obtained in laser-heated diamond anvil cells, using the speckle method as melting detection technique. They also confirm a flat slope of the melting line in the pressure range between 10 and 30 GPa. The flat melting curve is associated with the presence of the solid high-temperature body-centered cubic phase of calcium and to a small volume change between this phase and the liquid at melting. Reasons for the stabilization of the body-centered face at high-temperature conditions will be discussed.

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In situ characterization of the high pressure – high temperature melting curve of platinum

Scientific Reports ◽

10.1038/s41598-019-49676-y ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 21

Author(s):

Simone Anzellini ◽

Virginia Monteseguro ◽

Enrico Bandiello ◽

Agnès Dewaele ◽

Leonid Burakovsky ◽

...

Keyword(s):

Melting Curve ◽

Cubic Phase ◽

Face Centered Cubic ◽

Melting Line ◽

Diamond Anvil Cells ◽

High Pressure High Temperature ◽

The Face ◽

Diamond Anvil ◽

Face Centered ◽

Laser Heated

Abstract In this work, the melting line of platinum has been characterized both experimentally, using synchrotron X-ray diffraction in laser-heated diamond-anvil cells, and theoretically, using ab initio simulations. In the investigated pressure and temperature range (pressure between 10 GPa and 110 GPa and temperature between 300 K and 4800 K), only the face-centered cubic phase of platinum has been observed. The melting points obtained with the two techniques are in good agreement. Furthermore, the obtained results agree and considerably extend the melting line previously obtained in large-volume devices and in one laser-heated diamond-anvil cells experiment, in which the speckle method was used as melting detection technique. The divergence between previous laser-heating experiments is resolved in favor of those experiments reporting the higher melting slope.

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Defect Complexes and Non-Equilibrium Processes Underlying the P-Type Doping of GaN

MRS Proceedings ◽

10.1557/proc-537-g5.3 ◽

1998 ◽

Vol 537 ◽

Author(s):

Fernando A. Reboredo ◽

Sokrates T. Pantelides

Keyword(s):

High Temperature ◽

Experimental Evidence ◽

First Principles ◽

Final Anneal ◽

First Principles Calculations ◽

Defect Complexes ◽

Equilibrium Processes ◽

Open Questions ◽

High Temperature Anneal ◽

P Type

AbstractIt is well known that hydrogen plays a key role in p-type doping of GaN. It is believed that H passivates substitutional Mg during growth by forming a Mgs-N-Hi complex; in subsequent annealing, H is removed, resulting in p-type doping. Several open questions have remained, however, such as experimental evidence for other complexes involving Mg and H and difficulties in accounting for the relatively high-temperature anneal needed to remove H. We present first principles calculations in terms of which we show that the doping process is in fact significantly more complex. In particular, interstitial Mg plays a major role in limiting p-type doping. Overall, several substitutional/interstitial complexes form and can bind H, with vibrational frequencies that account for hitherto unidentified observed lines. We predict that these defects, which limit doping efficiency, can be eliminated by annealing in an atmosphere of H and N prior to the final anneal that removes H.

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In situ synchrotron X-ray diffraction with laser-heated diamond anvil cells study of Pt up to 95 GPa and 3150 K

RSC Advances ◽

10.1039/c4ra12769b ◽

2015 ◽

Vol 5 (19) ◽

pp. 14603-14609 ◽

Cited By ~ 2

Author(s):

Xiaoli Huang ◽

Fangfei Li ◽

Qiang Zhou ◽

Gang Wu ◽

Yanping Huang ◽

...

Keyword(s):

X Ray Diffraction ◽

Diamond Anvil Cells ◽

X Ray ◽

Diamond Anvil ◽

Laser Heated

In situ synchrotron X-ray diffraction with laser-heated diamond anvil cells study the EOS of Pt.

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Laser heating system at the Extreme Conditions Beamline, P02.2, PETRA III

Journal of Synchrotron Radiation ◽

10.1107/s1600577521009231 ◽

2021 ◽

Vol 28 (6) ◽

Author(s):

Zuzana Konôpková ◽

Wolfgang Morgenroth ◽

Rachel Husband ◽

Nico Giordano ◽

Anna Pakhomova ◽

...

Keyword(s):

Ray Tracing ◽

Laser Heating ◽

Melting Curve ◽

Heating System ◽

Laser Source ◽

Extreme Conditions ◽

Diamond Anvil Cells ◽

X Ray ◽

Diamond Anvil ◽

Pulsed Laser Heating

A laser heating system for samples confined in diamond anvil cells paired with in situ X-ray diffraction measurements at the Extreme Conditions Beamline of PETRA III is presented. The system features two independent laser configurations (on-axis and off-axis of the X-ray path) allowing for a broad range of experiments using different designs of diamond anvil cells. The power of the continuous laser source can be modulated for use in various pulsed laser heating or flash heating applications. An example of such an application is illustrated here on the melting curve of iron at megabar pressures. The optical path of the spectroradiometry measurements is simulated with ray-tracing methods in order to assess the level of present aberrations in the system and the results are compared with other systems, that are using simpler lens optics. Based on the ray-tracing the choice of the first achromatic lens and other aspects for accurate temperature measurements are evaluated.

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First principles calculations of structural and defect properties of high‐temperature intermetallics

Journal of the Chinese Institute of Engineers ◽

10.1080/02533839.1999.9670484 ◽

1999 ◽

Vol 22 (4) ◽

pp. 457-468

Author(s):

C. L. Fu

Keyword(s):

High Temperature ◽

First Principles ◽

First Principles Calculations

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Melting of iron determined by X-ray absorption spectroscopy to 100 GPa

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1502363112 ◽

2015 ◽

Vol 112 (39) ◽

pp. 12042-12045 ◽

Cited By ~ 41

Author(s):

Giuliana Aquilanti ◽

Angela Trapananti ◽

Amol Karandikar ◽

Innokenty Kantor ◽

Carlo Marini ◽

...

Keyword(s):

Melting Temperature ◽

Absorption Spectroscopy ◽

Inner Core ◽

Solid Phase ◽

Melting Curve ◽

X Ray ◽

Core Boundary ◽

Diamond Anvil ◽

Laser Heated ◽

X Ray Absorption

Temperature, thermal history, and dynamics of Earth rely critically on the knowledge of the melting temperature of iron at the pressure conditions of the inner core boundary (ICB) where the geotherm crosses the melting curve. The literature on this subject is overwhelming, and no consensus has been reached, with a very large disagreement of the order of 2,000 K for the ICB temperature. Here we report new data on the melting temperature of iron in a laser-heated diamond anvil cell to 103 GPa obtained by X-ray absorption spectroscopy, a technique rarely used at such conditions. The modifications of the onset of the absorption spectra are used as a reliable melting criterion regardless of the solid phase from which the solid to liquid transition takes place. Our results show a melting temperature of iron in agreement with most previous studies up to 100 GPa, namely of 3,090 K at 103 GPa.

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