Preparation of lanthanum hexaboride by electrolysis and measurements of the Raman-active phonons

Scholz, H.; Bauhofer, W.; Ploog, K.

doi:10.1016/0038-1098(76)90388-4

Cited by 25 publications

(7 citation statements)

References 3 publications

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“…We obtain (using GGA) a frequency of 1218 cm\ for the A 1g mode in LaB , which is in excellent agreement with the experimental result of 1245 cm\ (10). The E g phonon consists of an asymmetric breathing of the octahedra in x, y, and z directions, respectively.…”

Section: Frozen Phonon Calculationssupporting

confidence: 83%

Electronic Structure Calculations of Hexaborides and Boron Carbide

Ripplinger

Schwarz

Blaha

1997

Journal of Solid State Chemistry

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Section: Frozen Phonon Calculationssupporting

confidence: 83%

Electronic Structure Calculations of Hexaborides and Boron Carbide

Ripplinger

Schwarz

Blaha

1997

Journal of Solid State Chemistry

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“…The Raman spectra of metal hexaborides have been intensely investigated by many researchers . The dominant Raman‐active phonons in MB 6 (where M = Ca, Sr, Ba, Ce, La, Pr, Nd, Sm, Eu, Gd, Dy, and Yb, respectively) show A 1g , E g , and T 2g (or F 2g as used in article) symmetries that correspond to the breathing and deforming modes of the B 6 octahedral clusters . These modes are observed at about 1,300, 1,200, and 700 cm −1 , respectively, and completely satisfy the polarization selection rule for

italicPm \overset{3}{true} italicm

cubic symmetry.…”

Section: Discussionmentioning

confidence: 99%

“…[2,[18][19][20]26,[30][31][32][33][34][35][36]39,40,[51][52][53][54] The dominant Ramanactive phonons in MB 6 (where M = Ca, Sr, Ba, Ce, La, Pr, Nd, Sm, Eu, Gd, Dy, and Yb, respectively) show A 1g , E g , and T 2g (or F 2g as used in article [2] ) symmetries that correspond to the breathing and deforming modes of the B 6 octahedral clusters. [2,32,51] These modes are observed at about 1,300, 1,200, and 700 cm −1 , respectively, and completely satisfy the polarization selection rule for Pm3m cubic symmetry. In this symmetry, all Raman-active phonons appear in the (x + y, x + y) polarization geometry, [30] whereas A 1g is particularly apparent in the (x, x) geometry, E g in (x, x) and (x + y, x − y), and T 2g in (x, y), where x and y correspond to the [100] and [010] axes, respectively.…”

Section: Raman Spectroscopy Of Hexaboridesmentioning

confidence: 99%

Spectroscopy of metal hexaborides: Phonon dispersion models

Alarco

Shahbazi

Talbot

2018

J Raman Spectroscopy

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Raman spectroscopy of many metal hexaborides is well understood for vibrations of italicPmtrue3¯italicm symmetry that can be ascribed to the breathing and deforming modes of boron octahedral clusters at the corners of the cubic unit cell. However, the significance of the lower energy modes has been subject to debate wherein interpretation is dependent on “rattling” of the metal ion within the boron cage or on alternative mechanisms such as the presence of defects or of isotope clusters. Furthermore, converged calculations of phonon dispersions (PDs) using Density Functional Theory (DFT) for YB6 with italicPmtrue3¯italicm symmetry in the published literature are limited and equivocal. Converged PDs across all reciprocal lattice orientations are an important indicator of thermodynamic stability for a phase. We use this criterion to evaluate symmetry conditions for hexaboride structures and compare DFT models of PDs with Raman spectra for the hexaborides BaB6, LaB6, and YB6. We demonstrate that models with lower symmetry using a P4/mmm superlattice along one primary axial direction allow the lower energy modes to be assigned to a point symmetry. This approach, which models displacements of the metal position along the superlattice direction, results in a convergent PD for YB6, an outcome difficult to achieve with italicPmtrue3¯italicm symmetry.

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“…Here, A 1g and E g are B-B bond stretching modes and T 2g mode is a B-B-B valence angle bending mode of boron lattice. Raman band associated with T 2g mode shows a clear shoulder on the high frequency side and is attributed [11][12][13] to the most abundant isotopes of B, namely B 11 / B 10 . Accordingly, the observed lineshape is least square fitted to a sum of two Lorentzians with an area ratio of A 1 / A 2 ¼ 2.1:1 to take into account isotopic 11 B: 10 B abundance.…”

Section: Raman Scatteringmentioning

confidence: 98%

High pressure phase transition in metallic LaB6: Raman and X-ray diffraction studies

Teredesai¹,

Muthu²,

Chandrabhas³

et al. 2004

Solid State Communications

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High pressure Raman and angle dispersive X-ray diffraction (ADXRD) measurements on the metallic hexaboride LaB 6 have been carried out upto the pressures of about 20 GPa. The subtle phase transition around 10 GPa indicated in Raman measurements is confirmed by ADXRD experiments to be a structural change from cubic to orthorhombic phase. Ab-initio electronic band structure calculations using full potential linear augmented plane wave method carried out as a function of pressure show that this transition is driven by the interception of Fermi level by electronic band minimum around the transition pressure.

show abstract

Preparation of lanthanum hexaboride by electrolysis and measurements of the Raman-active phonons

Cited by 25 publications

References 3 publications

Electronic Structure Calculations of Hexaborides and Boron Carbide

Electronic Structure Calculations of Hexaborides and Boron Carbide

Spectroscopy of metal hexaborides: Phonon dispersion models

High pressure phase transition in metallic LaB6: Raman and X-ray diffraction studies

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