Can elemental bismuth be a liquid crystal?

Argaman, Nathan

doi:10.1016/j.physleta.2010.07.067

Cited by 10 publications

(6 citation statements)

References 43 publications

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“…Previous studies have suggested that this plateau is associated with a structural rearrangement in the liquid state. 20,24,25,26 We suggest that this phenomenology reflects a broad maximum in the sound velocity, analogous to that observed in liquid Sb and is typical to column V in the periodic table. To estimate the behavior of the sound velocity near the melting point, we have fitted the temperature dependence to a third-order polynomial (Fig.…”

Section: Liquid Pnictide Hypothesessupporting

confidence: 69%

Liquid structure and temperature invariance of sound velocity in supercooled Bi melt

Emuna

Mayo

Greenberg³

et al. 2014

The Journal of Chemical Physics

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Structural rearrangement of liquid Bi in the vicinity of the melting point has been proposed due to the unique temperature invariant sound velocity observed above the melting temperature, the low symmetry of Bi in the solid phase and the necessity of overheating to achieve supercooling. The existence of this structural rearrangement is examined by measurements on supercooled Bi. The sound velocity of liquid Bi was measured into the supercooled region to high accuracy and it was found to be invariant over a temperature range of ca. 60 degrees, from 35 degrees above the melting point to ca. 25 degrees into the supercooled region. The structural origin of this phenomenon was explored by neutron diffraction structural measurements in the supercooled temperature range. These measurements indicate a continuous modification of the short range order in the melt. The structure of the liquid is analyzed within a quasi-crystalline model and is found to evolve continuously, similar to other known liquid pnictide systems. The results are discussed in the context of two competing hypotheses proposed to explain properties of liquid Bi near the melting: (i) liquid bismuth undergoes a structural rearrangement slightly above melting (ii) liquid Bi exhibits a broad maximum in the sound velocity located incidentally at the melting temperature.2

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Section: Liquid Pnictide Hypothesessupporting

confidence: 69%

Liquid structure and temperature invariance of sound velocity in supercooled Bi melt

Emuna

Mayo

Greenberg³

et al. 2014

The Journal of Chemical Physics

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“…Indeed, undercooled liquid L by droplet emulsion forms metastable crystals at ambient condition with structure that is distinct from that of Bi-I but similar to that of the monoclinic Bi-II phase (44). It is, therefore, likely that this peak represents a remnant of the bilayer-like units in liquid L, consistent with the two-step liquid model (41). The irreversible liquid structure change above ∼1,250 K at 2.0 GPa indicates that, around this pressure and at temperatures deep in the liquid state, Bi possesses certain "memory" of the L structural units on cooling.…”

Section: Discussionmentioning

confidence: 54%

“…S1). Based on the complex interatomic binding in rhombohedral Bi-I, the 1-atm melting process has been postulated to occur in two discrete steps (41). The first step involves loosening of the adjacent bilayers, leading to a liquid crystal-like (or "smecticlike") liquid (L) near 544 K, while retaining the threefold rotational symmetry in the Bi4 motifs in the bilayers.…”

Section: Discussionmentioning

confidence: 99%

Deep melting reveals liquid structural memory and anomalous ferromagnetism in bismuth

Shu

Wang

et al. 2017

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

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As an archetypal semimetal with complex and anisotropic Fermi surface and unusual electric properties (e.g., high electrical resistance, large magnetoresistance, and giant Hall effect), bismuth (Bi) has played a critical role in metal physics. In general, Bi displays diamagnetism with a high volumetric susceptibility (∼10 −4 ). Here, we report unusual ferromagnetism in bulk Bi samples recovered from a molten state at pressures of 1.4-2.5 GPa and temperatures above ∼1,250 K. The ferromagnetism is associated with a surprising structural memory effect in the molten state. On heating, low-temperature Bi liquid (L) transforms to a more randomly disordered high-temperature liquid (L ) around 1,250 K. By cooling from above 1,250 K, certain structural characteristics of liquid L are preserved in L. Bi clusters with characteristics of the liquid L motifs are further preserved through solidification into the Bi-II phase across the pressure-independent melting curve, which may be responsible for the observed ferromagnetism.bismuth | high pressure | ferromagnetism | melt structure B ismuth (Bi) has played important roles in metal and condensed matter physics. The extremely low carrier density of Bi allows quantum limits of the Landau level to be studied under high magnetic field (1) and quantum size effects to be observed at ∼100-nm length scale (2). At ambient condition, Bi is known to crystallize in the rhombohedral A-7 type structure (space group R-3m, D 5 3d ), with the primitive unit cell containing two atoms at positions (u, u, u) and (−u, −u, −u). Each atom has three equidistant nearest neighbors tightly bonded at a distance of ∼3.062Å (3). The Bi4 motifs form puckered bilayers ( Fig. S1A) with a thickness of 1.59Å stacked along the rhombohedral [111] direction. The distance between adjacent bilayers is 2.35Å (4), slightly smaller than the next nearest distance of 3.512Å (5). Each atom's next nearest neighbors are in the adjacent bilayers, and the bonding within each bilayer is much stronger than the interbilayer bonding. As such, Bi exhibits rather complex interatomic binding, with coexisting covalent (within the bilayers), metallic, and weaker van der Waals-like (between bilayers) bonding (4).The phase diagram of Bi is rich and complex ( Fig. 1). At ambient pressure, Bi melts at 544 K (6) with a liquid-liquid transition at 1,010 K (7). With increasing pressure, Bi undergoes structural transitions in both solid and liquid states. The A-7 structured Bi-I phase transforms successively into the monoclinic (Bi-II), incommensurate host-guest (Bi-III), and body-centered cubic (Bi-V) phases (8-10) with increasing pressure to ∼6 GPa. On pressure release, these high-pressure metallic crystalline phases are unstable and revert to the Bi-I phase. Below ∼1.6 GPa, the melting temperature of Bi-I decreases with increasing pressure, a behavior similar to that of ice. Between 1.6 and 2.4 GPa (11), the solid just below melting is the Bi-II phase, which has a similar bilayer structure to that of Bi-I, except that the distance betwe...

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“…A particularly interesting question is the mechanism behind the LLPTs in bismuth. In fact, one of the present authors has speculated that the covalently-bonded bilayer sheets of crystalline bismuth become only partly disordered at melting (545 K), and fully disintegrate only at the LLPT at 1010 K. 59 This would mean that the phase obtained by melting of solid bismuth consists of 2D polymers (the bilayers), which are unable to pass through each other, but able to glide in the transverse directions, possibly becoming crumpled, thus adding to the disorder. This suggested mechanism also provides a reasonable context for explanation of the recently-observed anomalies of Refs.…”

Section: Summary and Discussionmentioning

confidence: 65%

Bond-counting potentials: A classical many-body model of covalent bonding with exact solutions in one dimension

Matityahu¹,

Argaman²

2019

Phys. Rev. E

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We introduce "bond-counting" potentials, which provide an elementary description of covalent bonding. These simplistic potentials are intended for studies of the mechanisms behind a variety of phase transitions in elemental melts, including the liquid-liquid phase transitions (LLPT) in phosphorus and bismuth. As a first study employing such potentials, an analytic solution of a onedimensional model system is presented, including its thermodynamic properties and its structure factor. In the simplest case, the chemical valency of each atom is 1, and either single atoms or diatomic molecules are present. At low temperatures and moderate pressures, the system consists almost exclusively of molecules, and single atoms act as topological defects. A slightly more complicated case involves a valency of 2, with either single or double bonding. This system exhibits a first-order LLPT from a molecular to a polymeric phase, as in phosphorus. In this case, the onedimensional model system exhibits phase separation for finite-sized systems at low temperatures. A variant of this system also exhibits a non-equilibrium phase transformation upon heating the molecular condensed phase, qualitatively similar to boiling in white phosphorus.

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Can elemental bismuth be a liquid crystal?

Cited by 10 publications

References 43 publications

Liquid structure and temperature invariance of sound velocity in supercooled Bi melt

Liquid structure and temperature invariance of sound velocity in supercooled Bi melt

Deep melting reveals liquid structural memory and anomalous ferromagnetism in bismuth

Bond-counting potentials: A classical many-body model of covalent bonding with exact solutions in one dimension

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