Pressure-induced AlB2to MgCu2-type structural transition in ThAl2

Godwal, B. K.; Vijaykumar, V.; Sikka, S. K.; Chidambaram, R.

doi:10.1088/0305-4608/16/10/010

Cited by 14 publications

(4 citation statements)

References 5 publications

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“…This crystal stabilizes in the AlB 2 -type structure and it transitates to the MgCu 2 structure by effect of pressure. 47,48 In this case, the solid-solid phase transition occurs in reverse order than in RG͑He͒ 2 solids because the Al-Al bonds turn out to be less compressible than the Th-Th ones ͓in RG͑He͒ 2 systems, RG-RG bonds are less compressible than He-He bonds͔. A similar behavior has been also found in YCu 2 .…”

Section: B Ar(he)supporting

confidence: 58%

High-pressure phases, vibrational properties, and electronic structure ofNe(He)2andAr
Cazorla
¹
,
Errandonea
²
,
Sola
³

2009
Phys. Rev. B
62
3
44
0
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We have carried out a comprehensive first-principles study of the energetic, structural, and electronic properties of solid rare-gas ͑RG͒-helium binary compounds, in particular, Ne͑He͒ 2 and Ar͑He͒ 2 , under pressure and at temperatures within the range of 0 Յ T Յ 2000 K. Our approach is based on density-functional theory and the generalized gradient approximation for the exchange-correlation energy; we rely on total Helmholtz freeenergy calculations performed within the quasiharmonic approximation for most of our analysis. In Ne͑He͒ 2 , we find that at pressures of around 20 GPa the system stabilizes in the MgZn 2 Laves structure, in accordance to what was suggested in previous experimental investigations. In the same compound, we predict a solid-solid phase transition among structures of the Laves family of the type MgZn 2 → MgCu 2 , at a pressure of P t = 120͑1͒ GPa. In Ar͑He͒ 2 , we find that the system stabilizes in the MgCu 2 Laves phase at low pressures but it transitates toward the AlB 2 -type structure by effect of compression at P t = 13.8͑4͒ GPa. The phonon spectra of the Ne͑He͒ 2 crystal in the MgZn 2 and MgCu 2 Laves structures, and that of Ar͑He͒ 2 in the AlB 2 -type phase, are reported. We observe that the compressibility of RG-RG and He-He bond distances in RG͑He͒ 2 crystals is practically identical to that found in respective RG and He pure solids. This behavior emulates that of a system of noninteracting hard spheres in closed-packed configuration and comes to show the relevance of short-range interactions on this type of mixtures. Based on size-ratio arguments and empirical observations, we construct a generalized phase diagram for all RG͑He͒ 2 crystals up to a pressure of 200 GPa where we map out systematic structural trends. Excellent qualitative agreement between such generalized phase diagram and accurate ab initio calculations is proved. A similar construction is done for RG͑H 2 ͒ 2 crystals; we find that the MgCu 2 Laves structure, which has been ignored in all RG-H 2 works so far, might turn out to be competitive with respect to the MgZn 2 and AlB 2 -type structures. Furthermore, we explore the pressure evolution of the energy-band gap in RG͑He͒ 2 solids and elaborate an argument based on electronic-band theory which explains the observed trends.

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Section: B Ar(he)supporting

confidence: 58%

High-pressure phases, vibrational properties, and electronic structure ofNe(He)2andAr
Cazorla
¹
,
Errandonea
²
,
Sola
³

2009
Phys. Rev. B
62
3
44
0
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“…The analysis of the associated splitting of the diffraction lines reveals that this distortion is orthorhombic and qualitatively the same as the already known distortion observed at low temperatures [161]. It is also interesting to note that in the structural map for AX 2 , the compound ThAl 2 , which crystallizes in the AlB 2 structure at ambient conditions, falls upon moderate compression in the region of Laves phase (MgCu 2 ) compounds [162]. The study of the high-pressure behavior of Laves structures has recently received a lot of attention because recent studies on CaLi 2 have predicted that it should be a very peculiar material under pressure.…”

Section: Ax 2 Compoundssupporting

confidence: 78%

Pressure‐induced structural phase transitions in materials and earth sciences

Manjón

Errandonea

2008

Physica Status Solidi (b)

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Pressure is an important thermodynamic parameter since it allows an increase of matter density by reducing volume. The reduction of volume by applying high pressures leads to an overall decrease of interatomic and intermolecular distances that allows exploring in detail atomic and molecular interactions. Therefore, high‐pressure research has improved our fundamental understanding of these interactions in solids, liquids and gasses. The study of the structure of matter under compression is a rapid developing field that is receiving increasing attention especially due to continuous experimental and theoretical developments. In this article, we give a brief description of the experimental and theoretical methods employed in the study of solid matter at high pressures and summarize the high‐pressure phases of the most relevant elements and inorganic compounds of the AX, A2X, AX2, ABX2, A2X3, ABX3, ABX4 and AB2X4 families giving an overview of the state of the art in high‐pressure research by highlighting recent discoveries, hot spots, controversial questions, and future directions of research. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…Since the study on the crystal structure of dicopper magnesium, MgCu 2 , was reported in 1938 by Hannawalt et al [1], many compounds have been found to be crystallized in the same cubic structure with space group Fd3m as in MgCu 2 [2][3][4][5][6][7][8][9][10]. This structure is commonly referred to as the MgCu 2 -type Laves phase [3][4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…This structure is commonly referred to as the MgCu 2 -type Laves phase [3][4][5][6][7][8][9][10]. For many years, the powder X-ray diffraction (XRD) data of Hannawalt et al [1] on MgCu 2 have been placed in the Powder Diffraction File (PDF) database with file #01-1226 [2] as the standard XRD pattern for crystal structure analysis or phase identification of materials.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and X-ray diffraction pattern for MgCu2

Liang

Tang

Fang

et al. 2006

Journal of Alloys and Compounds

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Pressure-induced AlB₂to MgCu₂-type structural transition in ThAl₂

Cited by 14 publications

References 5 publications

High-pressure phases, vibrational properties, and electronic structure ofNe(He)2andAr
Cazorla
¹
,
Errandonea
²
,
Sola
³

2009
Phys. Rev. B
62
3
44
0
View full text Add to dashboard Cite

High-pressure phases, vibrational properties, and electronic structure ofNe(He)2andAr
Cazorla
¹
,
Errandonea
²
,
Sola
³

2009
Phys. Rev. B
62
3
44
0
View full text Add to dashboard Cite

Pressure‐induced structural phase transitions in materials and earth sciences

Synthesis and X-ray diffraction pattern for MgCu2

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Pressure-induced AlB2to MgCu2-type structural transition in ThAl2

Cited by 14 publications

References 5 publications

High-pressure phases, vibrational properties, and electronic structure ofNe(He)2andArCazorla1, Errandonea2, Sola3 2009Phys. Rev. B623440View full textAdd to dashboardCite

High-pressure phases, vibrational properties, and electronic structure ofNe(He)2andArCazorla1, Errandonea2, Sola3 2009Phys. Rev. B623440View full textAdd to dashboardCite

Pressure‐induced structural phase transitions in materials and earth sciences

Synthesis and X-ray diffraction pattern for MgCu2

Contact Info

Product

Resources

About

Pressure-induced AlB₂to MgCu₂-type structural transition in ThAl₂

High-pressure phases, vibrational properties, and electronic structure ofNe(He)2andAr
Cazorla
¹
,
Errandonea
²
,
Sola
³

2009
Phys. Rev. B
62
3
44
0
View full text Add to dashboard Cite

High-pressure phases, vibrational properties, and electronic structure ofNe(He)2andAr
Cazorla
¹
,
Errandonea
²
,
Sola
³

2009
Phys. Rev. B
62
3
44
0
View full text Add to dashboard Cite