Pressure-induced phase transition in the cubic ScF3 crystal

Aleksandrov, K. S.; Voronov, V. N.; Vtyurin, A. N.; Крылов, А. С.; Мolokeev, Maxim S.; Pavlovskiĭ, M. S.; Goryaĭnov, S. V.; Likhacheva, A. Yu.; Анчаров, А. И.

doi:10.1134/s1063783409040295

Cited by 31 publications

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“…Although cubic ScF 3 transforms to a rhombohedral phase at a pressure of 0.6 GPa and then to another structure at about 3 GPa [18], the cubic DO 9 structure is robust over a wide range of temperatures at ambient pressure. The phase stability could be explained by the large vibrational entropy from the large-amplitude fluorine motions responsible for NTE.…”

Section: Prl 107 195504 (2011) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

“…1, and is stable from 10 to over 1600 K. Although À ReO 3 itself shows modest negative thermal expansion below 300 K [16,17], the NTE of ScF 3 is an order of magnitude larger. Only a small amount of work has been performed on the lattice dynamics of ScF 3 [18], although materials with a similar structure have been studied [19]. Here we report results from inelastic neutron scattering measurements of the lattice dynamics of ScF 3 from 7 to 750 K. The simplicity of the DO 9 structure of cubic ScF 3 allows a detailed analysis of the lattice dynamics, elucidating the connection between NTE and phonon anharmonicity.…”

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confidence: 94%

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Structural Relationship between Negative Thermal Expansion and Quartic Anharmonicity of CubicScF3

et al. 2011

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Cubic scandium trifluoride (ScF 3 ) has a large negative thermal expansion over a wide range of temperatures. Inelastic neutron scattering experiments were performed to study the temperature dependence of the lattice dynamics of ScF 3 from 7 to 750 K. The measured phonon densities of states show a large anharmonic contribution with a thermal stiffening of modes around 25 meV. Phonon calculations with first-principles methods identified the individual modes in the densities of states, and frozen phonon calculations showed that some of the modes with motions of F atoms transverse to their bond direction behave as quantum quartic oscillators. The quartic potential originates from harmonic interatomic forces in the DO 9 structure of ScF 3 , and accounts for phonon stiffening with the temperature and a significant part of the negative thermal expansion. DOI: 10.1103/PhysRevLett.107.195504 PACS numbers: 63.20.Ry, 63.20.DÀ, 65.40.De, 78.70.Nx Nearly all materials expand when heated, so exceptions are interesting. Negative thermal expansion (NTE) of a pure phase has attracted much attention over the past 20 years, driven both by curiosity, and by opportunities to design materials with special thermal properties. For materials like face-centered cubic plutonium and Invar alloys, NTE involves electronic or magnetic excitations. Other types of NTE are structure induced, originating from atom arrangements in the crystal [1]. Several mechanisms of NTE have been proposed, such as deformations of polyhedra, one-or two-dimensional NTE caused by normal thermal expansion of anisotropic bonds, NTE induced by interstitial cations, and NTE associated with transverse motions of linkage atoms (as in Fig. 1) [2,3]. Often NTE is anisotropic, and it usually occurs only in a small range of temperature [4]. Zirconium tungstate (ZrW 2 O 8 ) is a notable exception [5][6][7][8][9][10]. The NTE in ZrW 2 O 8 is associated with under-constrained atom sites in the crystal structure [11]. Although some of the behavior can be understood with a ''quasiharmonic'' model (a harmonic model with interatomic forces adapted to the bond lengths at a given temperature), anharmonic effects are expected, but the full connection between anharmonic lattice dynamics and NTE is obscured by the complexity of the structure [11]. Simplified models like a rigid square [12,13], a 3-atom Bravais lattice [11], and a rigid structure [14] have been used to explain the ''soft-phonon'' NTE mechanism, but accurate lattice dynamics for materials such as ZrW 2 O 8 are not easy to obtain from geometrical models.Very recently, a surprisingly large and isotropic negative thermal expansion was discovered in cubic scandium trifluoride (ScF 3 ) by Greve et al. [15]. It occurs over a wide range of temperature from 10 to about 1100 K, and exceeds À1:0 Â 10 À5 K À1 . Under ambient conditions, ScF 3 has the DO 9 crystal structure of -ReO 3 , shown in Fig. 1, and is stable from 10 to over 1600 K. Although À ReO 3 itself shows modest negative thermal expansion below 300 K [16,17], the ...

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Section: Prl 107 195504 (2011) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

mentioning

confidence: 94%

Structural Relationship between Negative Thermal Expansion and Quartic Anharmonicity of CubicScF3

et al. 2011

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“…Remarkably, using the observed pressure dependence of the transition temperature dT c /dp≃525 K/GPa [7,13,14], and the putative transition temperature T c ≃ − 39 K, one can estimate that pressures as small as 740 bar = 0.074 GPa would be sufficient to drive the transition upward to 0 K, permitting a clean manner in which to observe a structural quantum phase transition. The sensitivity of the phase boundary to these external changes suggests that the nature of the cubic phase is delicate at low temperature and susceptible to even mild perturbations.…”

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“…The c-r structural transition can be stabilized at finite temperature through substitution of other metals (Al, Ti, Y) for Sc, or in pure ScF 3 through application of very low hydrostatic pressures [13,14] (<0.2 GPa) at cryogenic temperatures. Remarkably, using the observed pressure dependence of the transition temperature dT c /dp≃525 K/GPa [7,13,14], and the putative transition temperature T c ≃ − 39 K, one can estimate that pressures as small as 740 bar = 0.074 GPa would be sufficient to drive the transition upward to 0 K, permitting a clean manner in which to observe a structural quantum phase transition.…”

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Large isotropic negative thermal expansion above a structural quantum phase transition

et al. 2015

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Perovskite structured materials contain myriad tunable ordered phases of electronic and magnetic origin with proven technological importance and strong promise for a variety of energy solutions. An always-contributing influence beneath these cooperative and competing interactions is the lattice, whose physics may be obscured in complex perovskites by the many coupled degrees of freedom, which makes these systems interesting. Here, we report signatures of an approach to a quantum phase transition very near the ground state of the nonmagnetic, ionic insulating, simple cubic perovskite material ScF 3 , and show that its physical properties are strongly effected as much as 100 K above the putative transition. Spatial and temporal correlations in the high-symmetry cubic phase determined using energy-and momentum-resolved inelastic x-ray scattering as well as x-ray diffraction reveal that soft mode, central peak, and thermal expansion phenomena are all strongly influenced by the transition. The class of materials with the perovskite structure and chemical formula ABX 3 contains examples of perhaps every possible type of physical behavior [1,2], much of which is difficult to understand because of the shear complexity of matter. A rich terrain of structural transitions associated with BX 6 octahedral tilting in perovskites strongly effects electronic conduction and magnetic exchange pathways, defining the framework of interactions governing a range of physical properties. The A-site tolerance appears to be an important parameter in determining the structural phase stability [1-3], but stable A-site-free perovskite structures are also thermodynamically stable. These are rare cases among oxides (X = O) because the B ions must take on rare hexavalent (+6) electronic configurations, and the only known instance is ReO 3 . In perovskites based on fluorine (X = F), however, the B ions assume the common trivalent (+3) configuration in an expanded suite of A-site-free perovskite lattices.Figure 1(a) shows a structural phase diagram of BF 3 perovskites, where B is a trivalent metal ion [4]. The 3d metal trifluorides display a reversible [5] structural cubic-torhombohedral (c-r) phase boundary. This sequence of 3d transition metal trifluoride compounds is rhombohedral at room temperature, with the exception of B = Sc, which appears at the zero-temperature terminated c-r phase boundary. Indeed, no rhombohedral phase transition has been observed for ScF 3 down to 0.4 K [6], suggesting that near this composition, the structural phase can be driven by a parameter other than temperature, implying that the ground state of this ionic insulator is very near a quantum phase transition (QPT). Cubic ScF 3 further stands out among substances in that it has the most stable structural phase of any known solid trifluoride, * Corresponding author: jason.hancock@uconn.edu retaining high cubic symmetry and a four-atom unit cell up to its high melting point, >1800 K [6,7]. Separate from the QPT reported here, further interest in this system is due t...

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Structural characteristics of radiation‐amorphized ZrSiO₄:U,Th according to Raman spectroscopy of Boson peak

Shchapova

Крылов

Votyakov

2023

J Raman Spectroscopy

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The structure of the amorphous fraction and the tensile-compressive stresses in amorphous-crystalline radiation-damaged zircon ZrSiO:U,Th depending on radiation dose and temperature (8-350 K) are investigated according to Raman spectroscopy of Boson peak for the first time. The Boson peak at 60-70 cm À1 associated with localized phonon states in the amorphous fraction ( f a ) is recorded at low temperatures (T < 100 K) for samples with f a < 30% and over the entire temperature range 8-350 K for f a > 70%. The wider localized states distribution in the latter case is considered as a sign of the amorphous phase structure evolution with an increase in radiation dose. The estimates of an atomic correlation radius based on the Ioffe-Regel criterion are similar to those in glasses, R c 2:0 À 2:3 nm. The monotonic increase in R c value during heating of zircon with f a > 70% is governed by thermal expansion of the percolating amorphous fraction. The nonmonotonic variations of the R c value in zircon with f a < 30% is determined by the stresses in the amorphous fraction due to the mismatch in thermal expansion coefficient (CTE) and elastic moduli of the amorphous and crystalline phases depending on temperature; a change in the sign of the crystalline fraction CTE at 30 K is assumed. The Boson peak disappearance at 100 K in zircon with f a < 30% during heating conforms to with the violation of the phonon localization as a consequence of amorphous fraction contraction and partial ordering. The data obtained are important for predicting the thermal and mechanical properties of heterogeneous radiationdamaged materials and nanocomposites.

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Pressure-induced phase transition in the cubic ScF3 crystal

Cited by 31 publications

References 9 publications

Structural Relationship between Negative Thermal Expansion and Quartic Anharmonicity of CubicScF3

Structural Relationship between Negative Thermal Expansion and Quartic Anharmonicity of CubicScF3

Large isotropic negative thermal expansion above a structural quantum phase transition

Structural characteristics of radiation‐amorphized ZrSiO₄:U,Th according to Raman spectroscopy of Boson peak

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Pressure-induced phase transition in the cubic ScF3 crystal

Cited by 31 publications

References 9 publications

Structural Relationship between Negative Thermal Expansion and Quartic Anharmonicity of CubicScF3

Structural Relationship between Negative Thermal Expansion and Quartic Anharmonicity of CubicScF3

Large isotropic negative thermal expansion above a structural quantum phase transition

Structural characteristics of radiation‐amorphized ZrSiO4:U,Th according to Raman spectroscopy of Boson peak

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Structural characteristics of radiation‐amorphized ZrSiO₄:U,Th according to Raman spectroscopy of Boson peak