X-ray Diffraction Study of Liquid Cs up to 9.8 GPa

Falconi, S.; Lundegaard, L. F.; Hejny, Clivia; McMahon, M. I.

doi:10.1103/physrevlett.94.125507

Cited by 70 publications

(61 citation statements)

References 22 publications

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“…Degtyareva [4] summarized all the sequences of structural transformations on pressure increase for each alkali element. In the work of Falconi et al [5], the phase diagram of cesium is presented in the (T ,P) plane. The Cs melting curve shows drastic changes in slope with pressure.…”

Section: Phase Diagrammentioning

confidence: 99%

“…However, published experimental and ab-initio studies do not specify the density values as a function of T and P. Knowledge of the density values is needed because above a given pressure, the physical properties of liquid potassium and cesium are expected to change, namely above 19 GPa [6] and 3.9 GPa [5], respectively. The potential we used to describe the atomic interactions is a priori not able to account for these changes.…”

Section: Phase Diagrammentioning

confidence: 99%

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Shear Viscosity of Liquid Potassium and Cesium: a Simulation Study

Meyer

Wax

2017

EPJ Web Conf.

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Abstract. The density and temperature dependences of the shear viscosity of liquid potassium and cesium are studied. The stress autocorrelation function is calculated from equilibrium molecular dynamics simulations. Using the GreenKubo formula, the shear viscosity is obtained. Interionic interactions are calculated by Fiolhais potential and are validated by comparison between simulation and experimental data along the liquid-gas coexistence curve for K and Cs. For both metals, three isochors and one isotherm are investigated. The recently proposed relation in [Phys. Rev. B 93, 214203 (2016)] is tested in the cases of K and Cs and it appears that this function reproduces qualitatively and quantitatively well the behavior of each element.

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Section: Phase Diagrammentioning

confidence: 99%

Section: Phase Diagrammentioning

confidence: 99%

Shear Viscosity of Liquid Potassium and Cesium: a Simulation Study

Meyer

Wax

2017

EPJ Web Conf.

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“…With further increases in pressure there is a second discontinuity, near 370-390GPa, interpreted as shock melting. [24] have reported X-ray diffraction measurements in liquid Cs in which they observed a discontinuity in the density above 3.9 GPa, to a liquid with a coordination number of about 8, which they suggest results from dsp 3 electronic hybridization. The alkali metals are known to form stable spherical clusters according to magic sizes corresponding to N=2, 8,18, 20, 40, 58, ….. electrons, just like electrons in the inert gas atoms [25].…”

Section: Free Energy Modelmentioning

confidence: 99%

Melting of bcc transition metals and icosahedral clustering

Ross

Boehler

Japel

2006

Journal of Physics and Chemistry of Solids

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In contrast to polyvalent metals, transition metals have low melting slopes(dT/dP) that are due to partially filled d-bands that allow for a lowering of liquid phase energy through s-d electron transfer and the formation of local structures. In the case of bcc transition metals we show the apparent discrepancy of DAC melting measurements with shock melting of Mo can be understood by reexamining the shock data for V and Ta and introducing the presence of an icosahedral short range order (ISRO) melt phase.

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“…Since, with few exceptions, transition metals do not undergo solid-solid phase changes along the melting curve, a sudden decrease in the melting slope implies an increase in the liquid density and an increase of the communal entropy, which may be attributed to an LLPT. In the case of Cs, which has 5d-electron character, and in a broad sense may be considered as a very early transition metal, Falconi et al [23,24] have interpreted structural changes and density increases from x-ray diffraction patterns above 3.9 GPa that mark the change from a simple to a locally complex liquid. Their analysis "strongly suggests the existence of dsp 3 electronic hybridization", a P/JT distortion.…”

mentioning

confidence: 99%

“…In the case of Cs, which has 5d-electron character, and in a broad sense may be considered as a very early transition metal, Falconi et al [23,24] have interpreted structural changes and density increases from x-ray diffraction patterns above 3.9 GPa that mark the change from a simple to a locally complex liquid. Their analysis "strongly suggests the existence of dsp 3 electronic hybridization", a P/JT distortion.…”

mentioning

confidence: 99%

Evidence for Liquid-Liquid Phase Transitions in the Transition Metals

Ross¹,

Errandonea²,

Boehler³

2008

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In this paper we report the first experimental evidence for the existence of a liquid-liquid phase transition(LLPT) in the transition metals. The transition is evident from discontinuities in the melting slope measured at high pressure. The discovery of LLPTs constitutes the strongest evidence for the presence of polymorphic structures in transition metal liquids at high pressure, and confirms the thesis that they are responsible for the relatively low melting temperatures, low melting slopes, and unusual phase diagrams. PACS number(s): 62. 50, 64.70.Ja, 64.70.Dv In earlier reports [1,2] we proposed that, in order to explain the apparent discrepancy between the diamond anvil and shock wave melting measurements of Mo and Ta, a liquid-liquid phase transition(LLPT), or liquid-glass transition, had to be present in the phase diagram. LLPTs are characterized by liquids of the same composition, but with different densities, and different atomic configurations, often referred to as polymorphs.In this paper we present the first experimental evidence for LLPTs in transition metals.It is now well established that elements with partially filled p-electron valence shells have directional bonding and exhibit an LLPT. Some examples are carbon [3,4], silicon [5,6], nitrogen [7,8] and phosphorous [9,10]. Bellisent et al.[11] interpreted the structure of liquid As, obtained from neutron diffraction experiments, as the consequence of a strong Peierles distortion in the half-filled 3p-band [12].The partially filled d-electron bands of transition metals also have the potential for a Peierles distortion, and directional bonding. The low melting slopes of transition metals has been attributed to directional d-electron bonding leading to the formation of 2 preferred local structures with five-fold icosahedral or polytetrahedral short range order(ISRO) resulting from Peierls/Jahn-Teller(P/JT) distortions [12,13]. Evidence for the presence of ISROs in transition metal liquids is now well documented and are referenced in our earlier reports [1,2]. ISROs introduce geometric frustration inhibiting solidification, and their presence as soluble impurities increases the communal entropy, further favoring the liquid stability and lowering the freezing temperature. Since ISROs are denser than the pure atomic liquid, pressure enhances the concentration of local structures. Therefore, it should come as no surprise, that pure non-alloyed transition metal liquids, with partially filled d-bands, exhibit polymorphic behavior, and a pressure-induced LLPT.The scarcity of experimental evidence for LLPTs in transition metals is at least partially due to the relatively high temperatures characteristic of these liquids. With the advent of the laser-heated diamond-anvil-cell technique it has now become possible to access melting curves of transition metals up to nearly 200 GPa and 4000K. The experimental method employed on a wide variety of solids, including on the transition metals, has been described and referenced in earlier reports [14][15][16][17]....

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X-ray Diffraction Study of Liquid Cs up to 9.8 GPa

Cited by 70 publications

References 22 publications

Shear Viscosity of Liquid Potassium and Cesium: a Simulation Study

Shear Viscosity of Liquid Potassium and Cesium: a Simulation Study

Melting of bcc transition metals and icosahedral clustering

Evidence for Liquid-Liquid Phase Transitions in the Transition Metals

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