High pressure–high temperature phase diagram of ammonia

Ninet, Sandra; Datchi, F.

doi:10.1063/1.2903491

Cited by 43 publications

(44 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We also used advanced filtering techniques for x-ray diffraction in the DAC in order to detect the appearance of the weak and the broad liquid signal at melting. Our x-ray based melting points of NH 3 agree well with the extrapolation of the melting data of Ninet and Datchi 24 and do not present the turnover reported by Ojwang et al 26 . We also do not find evidence for the new solid structures observed by Ojwang et al 26 GM -gold plated mirror LS -ZnSe lens M -mirror F -neutral filter SW -Schwarzschild objective BS -beam splitter CO 2 beam X-ray beam Camera FIG. 2.…”

Section: Introductionsupporting

confidence: 91%

“…There exists only few experimental investigations of the melting curve of ammonia above 300 K. In 1980, Hanson and Jordan 23 reported measurements up to 373 K and 2 GPa. In 2008, Ninet and Datchi 24 extended the determination to 9 GPa and 900 K using resistive heating in a diamond anvil cell (DAC). The melting temperature increases in a monotonous fashion with pressure and is well fitted by the Simon-Glatzel equation 25 , typical for weakly-bonded molecular systems.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Melting curve and chemical stability of ammonia at high pressure: Combined x-ray diffraction and Raman study

et al. 2019

View full text Add to dashboard Cite

The melting curve and stability of ammonia (NH3) is investigated up to 40 GPa and 3500 K by x-ray diffraction and Raman spectroscopy in the laser-heated diamond anvil cell. The NH3 samples were directly heated by the 10.6 µm radiation of a CO2 laser to reduce the risks of chemical reactions. Melting was unambiguously detected by the appearance of the liquid diffraction signal upon temperature increase. The melting temperature of NH3 is found to steadily increase with pressure up to 40 GPa, and the previously reported turnover is not observed. As a result, the melting line of NH3 is expected to cross the isentropes of Neptune and Uranus in the pressure range 55-65 GPa, implying the possible presence of superionic solid NH3 in these planets. Our x-ray and Raman measurements confirm the appearance of N2 and H2 upon heating the liquid phase from 6 to 40 GPa. But while the equilibrium 2N H3 N2 + 3H2 balances towards the dissociated elements at low pressure and high temperature, ammonia is found to the more stable species in the range 20-40 GPa, 300-3000 K.

show abstract

Section: Introductionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Melting curve and chemical stability of ammonia at high pressure: Combined x-ray diffraction and Raman study

et al. 2019

View full text Add to dashboard Cite

show abstract

“…17͒ or a discontinuity on the III-IV transition line at the expected triple point. 21 A large isotopic effect has also been reported: the transition has been observed at 12 and 18 GPa, respectively, for NH 3 and ND 3 at The main purpose of this study is to determine the structure of ammonia, including the positions of the H atoms, to pressures higher than the IV-V phase transition. This has been achieved by performing powder neutron-diffraction experiments at room temperature.…”

mentioning

confidence: 89%

Hydrogen bonding inND3probed by neutron diffraction to 24 GPa

et al. 2009

Self Cite

View full text Add to dashboard Cite

The structure of deuterated ammonia has been determined as a function of pressure up to 24 GPa using powder neutron-diffraction techniques. The presence of an isostructural transition at approximately 18 GPa is confirmed and ascribed to a slight displacement of one D atom. As a result, the H bond formed by this D atom changes angle and becomes nearly straight ͑178°͒ at 24 GPa. A departure from the molecular C 3v symmetry is also detected which is further supported by the evolution of the Raman spectra.

show abstract

“…In the case of water and ammonia, both experimental and computational studies at high pressure and temperature have been extensively pursued. [3][4][5] By contrast, the understanding of methane under these conditions is much less well established, with not even the density definitively known above 5 GPa.…”

Section: Introductionmentioning

confidence: 99%

The distorted close-packed crystal structure of methane A

Maynard-Casely

Bull

Guthrie

et al. 2010

The Journal of Chemical Physics

View full text Add to dashboard Cite

We have determined the full crystal structure of the high-pressure phase methane A. X-ray single-crystal diffraction data were used to determine the carbon-atom arrangement, and neutron powder diffraction data from a deuterated sample allowed the deuterium atoms to be located. It was then possible to refine all the hydrogen positions from the single-crystal x-ray data. The structure has 21 molecules in a rhombohedral unit cell, and is quite strongly distorted from the cubic close-packed structure of methane I, although some structural similarities remain. Full knowledge of this structure is important for modeling of methane at higher pressures, including in relation to the mineralogy of the outer solar system. We discuss interesting structural parallels with the carbon tetrahalides.

show abstract

High pressure–high temperature phase diagram of ammonia

Cited by 43 publications

References 39 publications

Melting curve and chemical stability of ammonia at high pressure: Combined x-ray diffraction and Raman study

Melting curve and chemical stability of ammonia at high pressure: Combined x-ray diffraction and Raman study

Hydrogen bonding inND3probed by neutron diffraction to 24 GPa

The distorted close-packed crystal structure of methane A

Contact Info

Product

Resources

About