Abstract:Due to discrepancies in the literature data the thermodynamic properties of liquid gallium are still in debate. Accurate measurements of adiabatic sound velocities as a function of pressure and temperature have been obtained by the combination of laser picosecond acoustics and surface imaging on sample loaded in diamond anvil cell. From these results the thermodynamic parameters of gallium have been extracted by a numerical procedure up to 10 GPa and 570 K. It is demonstrated that a Murnaghan equation of state… Show more
“…As expected due to densification under pressure, Q
1 shifts towards higher Q values and r
1 shifts to shorter distances with increasing pressure. Both the first peak position Q
1 and the nearest-neighbor distance r
1 change linearly as a function of pressure, suggesting that no detectable liquid-liquid phase transition occurs in this pressure range, which is consistent with previous studies 25, 26 .Figure 1( a ) Structure factors S ( Q ) and ( b ) pair distribution function g ( r ) from experiments (blue thin line) at various pressure conditions and corresponding RMC simulations (gray thick line). Crystalline structure of Ga phase I, II and III are illustrated in their corresponding phase domains.…”
In situ high energy X-ray pair distribution function (PDF) measurements, microtomography and reverse Monte Carlo simulations were used to characterize the local structure of liquid gallium up to 1.9 GPa. This pressure range includes the well-known solid-solid phase transition from Ga-I to Ga-II at low temperature. In term of previous research, the local structure of liquid gallium within this domain was suggested a mixture of two local structures, Ga I and Ga II, based on fitting experimental PDF to known crystal structure, with a controversy. However, our result shows a distinctly different result that the local structure of liquid gallium resembles the atomic arrangement of both gallium phase II and III (the high pressure crystalline phase). A melting mechanism is proposed for Ga, in which the atomic structure of phase Ι breaks up at the onset of melting, providing sufficient free volume for atoms to rearrange, to form the melt.
“…As expected due to densification under pressure, Q
1 shifts towards higher Q values and r
1 shifts to shorter distances with increasing pressure. Both the first peak position Q
1 and the nearest-neighbor distance r
1 change linearly as a function of pressure, suggesting that no detectable liquid-liquid phase transition occurs in this pressure range, which is consistent with previous studies 25, 26 .Figure 1( a ) Structure factors S ( Q ) and ( b ) pair distribution function g ( r ) from experiments (blue thin line) at various pressure conditions and corresponding RMC simulations (gray thick line). Crystalline structure of Ga phase I, II and III are illustrated in their corresponding phase domains.…”
In situ high energy X-ray pair distribution function (PDF) measurements, microtomography and reverse Monte Carlo simulations were used to characterize the local structure of liquid gallium up to 1.9 GPa. This pressure range includes the well-known solid-solid phase transition from Ga-I to Ga-II at low temperature. In term of previous research, the local structure of liquid gallium within this domain was suggested a mixture of two local structures, Ga I and Ga II, based on fitting experimental PDF to known crystal structure, with a controversy. However, our result shows a distinctly different result that the local structure of liquid gallium resembles the atomic arrangement of both gallium phase II and III (the high pressure crystalline phase). A melting mechanism is proposed for Ga, in which the atomic structure of phase Ι breaks up at the onset of melting, providing sufficient free volume for atoms to rearrange, to form the melt.
“…Moreover, by white light interferences, we also estimated the thickness of the recovered gasket at ambient conditions to be 21(1)µm. A constant thickness upon decompression is consistent with many other experimental observations 22,25,26 and has been explained through the study of plasticity processes inside the rhenium gasket 27 under relaxing stresses.…”
Section: Experimental Methodssupporting
confidence: 90%
“…As illustrated in Fig. 3, the evolution of the liquid density with pressure along an isotherm at 500 K (extracted from the present sound velocity measurements on the basis of exact thermodynamic relations, an approach that have been already proven for many different metallic liquids 22,26 ) overall well compares with most recent density determination by x-ray absorption technique 19 , at least to the extent that any sharp discontinuity in density is Hattori 19 ). The maximal uncertainties associated with the relative densities ∆ρ/ρ is estimated of about 2% 22,26 .…”
Liquid cesium (l-Cs) sound velocity at high densities was investigated along a 500 K isotherm using high-pressure picosecond acoustics measurements. At 2.0 GPa, the liquid sound velocity goes through a maximum versus pressure without any change on the reflectivity and interferometry acoustic signals. Upon further compression, a softening of the l-Cs visco-elastic properties is observed from 2.0 up to 4.0 GPa, pressure at which the reflectometric signal is abruptly reversed whereas the interferometric signal remains qualitatively the same. This anomalous behaviour could be related to an electronic transformation within the l-Cs state, which here again could reflect what happens at lower temperature within the solid state. If so, such liquid-liquid transition may be driven by the progressive collapse of the 6s electronic orbital onto the 5d ones. Above 4.0 GPa, the l-Cs sound velocity starts again to increase as commonly expected upon compression.
“…The investigation of phase transformations is performed with two complementary in situ techniques: Raman scattering technique and picosecond acoustics technique. The latter is equivalent to time-resolved Brillouin spectroscopy, and it exploits the sound velocity as a sensitive tool to probe the phase changes in material [17].…”
Lauric acid is commonly used as a coating agent which efficiently protects against oxidation and/or coalescence a set of inorganic nanocrystals obtained by chemical process. Its stability under pressure is likely to be informative on the stability and ordering of compressed supercrystals of nanocrystals. Therefore the elastic behaviour of lauric acid submitted to high pressures up to 25 GPa is studied. This elastic behavior has been probed by two complementary in situ techniques at high pressure : Raman spectroscopy and picosecond acoustics. Comparison between pressure-induced transformations as observed with the two techniques suggests that lauric acid remains elastically stable above 2 GPa up to 25 GPa.
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