Transverse Acoustic Excitations in Liquid Ga

Hosokawa, Shinya; Inui, Masanori; Kajihara, Y.; Matsuda, Kazuhiro; Ichitsubo, Tetsu; Pilgrim, W.‐C.; Sinn, H.; González, L.; González, D. J.; Tsutsui, Satoshi; Baron, Alfred Q. R.

doi:10.1103/physrevlett.102.105502

Cited by 156 publications

(175 citation statements)

References 17 publications

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“…3 shows that acoustic excitations with transverse polarization are present in the liquid for q∕q 0 ≥ 0.2. Qualitative similar observations have already been reported in other liquids (5,7,27). The striking result of Fig.…”

Section: Resultssupporting

confidence: 91%

“…This broadening is generally related to the distribution of local structures that is present in the liquid phase (4) and that is, e.g., characterized by the distribution of first neighbors distances. Collective excitations exist as well in liquids, and their broadening is usually attributed to relaxation processes (5)(6)(7). In fact, the response of a crystal to an external perturbation can be formally expressed in terms of phonons, the modes of lattice vibration that can be defined in presence of a long-range, periodic structure.…”

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confidence: 99%

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Fingerprints of order and disorder on the high-frequency dynamics of liquids

Giordano

Monaco

2010

Proc. Natl. Acad. Sci. U.S.A.

120

133

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It is largely accepted that liquids are characterized by a short-range order usually corresponding to that of the solid phase at the same density. It is less clear to what extent dynamic properties of liquids and crystals can be compared. In particular, high-frequency collective excitations reminiscent of phonons in solids exist as well in liquids. They are however traditionally discussed in terms of relaxation processes characteristic of the liquid phase. We report here on a quantitative comparison of the collective excitations in liquid and polycrystalline sodium. We show that liquid sodium exhibits acoustic excitations of both longitudinal and transverse polarization at frequencies strictly related to those of the corresponding crystal. The only relevant difference between the liquid and the polycrystal appears in the broadening of the excitations: An additional disorder-induced contribution comes into play in the case of the liquid, which we show to be related to the distribution of local structures around the average one. These results establish a direct connection between structural and dynamic properties of liquids, with shortrange order and overall structural disorder leaving very specific fingerprints.vibrational dynamics | X-ray scattering T he short-range order in liquids, characterized by parameters like, e.g., the first neighbors distance and number, is usually similar to that of the corresponding solids (1, 2). Ab initio calculations of liquid structures spanning a large density range do support this idea (3). For what concerns dynamic properties, the situation is more complex. Local vibrations appear in the liquid as in the corresponding solid, although they are usually much broader (1). This broadening is generally related to the distribution of local structures that is present in the liquid phase (4) and that is, e.g., characterized by the distribution of first neighbors distances. Collective excitations exist as well in liquids, and their broadening is usually attributed to relaxation processes (5-7). In fact, the response of a crystal to an external perturbation can be formally expressed in terms of phonons, the modes of lattice vibration that can be defined in presence of a long-range, periodic structure. In liquids this description is instead formally not appropriate, and the concept of relaxation is usually introduced with reference to a dynamic process that controls the reequilibration of the system after it has been perturbed (8). Several distinct relaxation processes can be introduced to describe the dynamics of liquids, each one characterized by a characteristic time, τ, that sets the timescale over which it is active and observable. Indeed, if the perturbation frequency, ω, is such that ωτ ≪ 1, the relaxation is active, whereas when ωτ ≫ 1 the relaxation process does not have the time to take place and is frozen. In the infinite frequency limit, where all relaxations are frozen, the liquid behaves like a solid: This limit corresponds to the elastic regime, where only the instantaneous ...

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Section: Resultssupporting

confidence: 91%

mentioning

confidence: 99%

Fingerprints of order and disorder on the high-frequency dynamics of liquids

Giordano

Monaco

2010

Proc. Natl. Acad. Sci. U.S.A.

120

133

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“…Another important and so far unclear issue is the range of wave numbers where the manifestation of the second branch of transverse excitations can be observed. As a matter of fact, analysis of inelastic X-ray scattering experiments indicated a possible coupling between longitudinal (L) and transverse (T) collective excitations and consequently two contributions of coupled propagating modes at relatively small wave numbers [7]. In contrast, ab initio MD (AIMD) simulations [4] clearly indicated the emergence of the second transverse branch only for wave numbers outside the first pseudo-Brillouin zone.…”

Section: Introductionmentioning

confidence: 99%

A Search for Two Types of Transverse Excitations in Liquid Polyvalent Metals at Ambient Pressure: An Ab Initio Molecular Dynamics Study of Collective Excitations in Liquid Al, Tl, and Ni

et al. 2018

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Recent findings of pressure-induced emergence of unusual high-frequency contribution to transverse current spectral functions in several simple liquid metals at high pressures raised a question whether similar features can be observed in liquid metals at ambient conditions. We report here analysis of ab initio molecular dynamics-derived longitudinal and transverse current spectral functions and corresponding dispersions of collective excitations in liquid polyvalent metals Al, Tl, Ni. We have not found evidences of the second branch of high-frequency transverse modes in liquid Al and Ni, while in the case of liquid Tl they were clearly present in transverse dynamics. The vibrational density of states for liquid Tl has a pronounced high-frequency shoulder, which is located right in the frequency range of the second high-frequency transverse branch, while for liquid Al and Ni the vibrational density of states has only a weak indication of possible high-frequency shoulder. The origin of specific behavior of transverse excitations in liquid Tl is discussed.

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“…However, a discussion has been opened a few years ago when Hosokawa and co-workers [11] claimed anomalies in their measurements of Ga. This anomaly for wave numbers inside the first pseudo-Brillouin zone has also been reported in Na [12], Sn [13], Cu, Fe [14], and Zn [15].…”

Section: Longitudinal/transverse Couplingmentioning

confidence: 93%

Analyzing the dynamic structure of liquid metals and alloys

Wax

Bryk

2017

EPJ Web Conf.

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Abstract. Experimental and numerical improvements have stimulated a great interest in the dynamic structure of liquids during the last decades. Many unexpected features have been unveiled among which fast sound, positive dispersion and possible coupling between transverse and longitudinal excitations can be mentioned. Models used to analyze these data have to be sound and more and more rigorous. In this study, we discuss the capability of a recently proposed fitting scheme (Wax J.

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Transverse Acoustic Excitations in Liquid Ga

Cited by 156 publications

References 17 publications

Fingerprints of order and disorder on the high-frequency dynamics of liquids

Fingerprints of order and disorder on the high-frequency dynamics of liquids

A Search for Two Types of Transverse Excitations in Liquid Polyvalent Metals at Ambient Pressure: An Ab Initio Molecular Dynamics Study of Collective Excitations in Liquid Al, Tl, and Ni

Analyzing the dynamic structure of liquid metals and alloys

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