Comparison of empirical bond-valence and first-principles energy calculations for a complex structural instability

Etxebarria, I.; Perez-Mato, J. M.; Garcı́a, Alberto; Blaha, Peter; Schwarz, K.; Rodriguez-Carvajal, J.

doi:10.1103/physrevb.72.174108

Cited by 27 publications

(24 citation statements)

References 23 publications

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“…31 More specifically, energy variations have been compared with corresponding changes in the so-called global instability index, 32 which measures the chemical stress in a structure. The striking similarity in the behavior of both quantities for unstable distortion modes of the parent high-symmetry configuration, which has also been reported in other systems, 34,35 is again observed in these two ferroic compounds.…”

Section: Discussionsupporting

confidence: 82%

“…34,35 ͒ This represents a new example of the ability of G ii 2 to closely mimic changes of the energy, particularly for low-energy or unstable primary distortion modes. 34,35 Note, however, that the agreement is not good for the M 3 -1q mode. The energy variation with amplitude of this secondary mode, depicted in Fig.…”

Section: Structural Instabilities In Sral 2 Omentioning

confidence: 95%

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Distortion modes and related ferroic properties of the stuffed tridymite-type compoundsSrAl2O4andBaAl2
Perez-Mato
¹
,
Withers
²
,
Larsson
³

et al. 2009
Phys. Rev. B
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The structural and associated ferroic properties of the stuffed tridymite-type compounds BaAl 2 O 4 and SrAl 2 O 4 have been investigated by means of ab initio calculations. Structures and energy landscapes have been analyzed in terms of symmetry-adapted distortion modes. Despite their rather different room-temperature symmetries, a triply-degenerate unstable antiferrodistortive rigid unit mode ͑RUM͒ of the Al 2 O 4 tetrahedral framework is shown to be the dominant instability for both compounds. An orthorhombic configuration resulting from a single wave ͑1q͒ distortion mode competes with a hexagonal configuration resulting from three superposed such waves ͑3q͒. The very small energy difference between these two configurations in the case of BaAl 2 O 4 would explain the recent electron microscope observation of orthorhombic symmetry on the nanoscale. A second unstable mode of polar character ͑also a RUM for the tetrahedral framework͒ is also present. While this second instability is too weak to condense in BaAl 2 O 4 , in the case of SrAl 2 O 4 it is fundamental to make the 1q configuration prevail. The condensation of this additional instability is the cause of the symmetry reduction in SrAl 2 O 4 to monoclinic. In contrast with previous literature, SrAl 2 O 4 is a proper ferroelectric and a pseudoproper ferroelastic, with an uncommon bilinear coupling between its spontaneous polarization and shear monoclinic strain. One expects direct switching of spontaneous polarization through a shear stress, and conversely switching of the ferroelastic spontaneous shear strain through an electric field. This property must be related to the elasticoluminescent and electroluminiscent properties reported in Eu-doped SrAl 2 O 4 . The calculated energy maps have been systematically compared with variations in the so-called global instability index, introduced within the empirical bond valence model. The similarity of the variation in both quantities ͑for the most unstable distortion modes͒ reported in other systems is also observed here.

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Section: Discussionsupporting

confidence: 82%

Section: Structural Instabilities In Sral 2 Omentioning

confidence: 95%

Distortion modes and related ferroic properties of the stuffed tridymite-type compoundsSrAl2O4andBaAl2
Perez-Mato
¹
,
Withers
²
,
Larsson
³

et al. 2009
Phys. Rev. B
Self Cite
37
3
19
0
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“…The Gii 2 and energy maps could be approximately related through a single scale factor of 500 mRy per square valence unit. 24 Here, we present a similar comparison for some of the critical modes of Bi 4 Ti 3 O 12 discussed above.…”

Section: Appendix: the Bond-valence Global Instability Indexmentioning

confidence: 77%

“…24 for the low-lying modes of SBT is maintained for Bi 4 Ti 3 O 12 . These calculations are presented in the Appendix.…”

Section: Computational Detailsmentioning

confidence: 85%

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Multiple instabilities inBi4Ti3O12: A ferroelectric beyond the soft-mode paradigm

et al. 2008

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The Aurivillius compound Bi 4 Ti 3 O 12 exhibits a single phase transition from a tetragonal high-temperature phase to a ferroelectric state. By means of first-principles calculations guided by a complete symmetry analysis of the experimental distortion, we confirm B1a1 as the ͑monoclinic͒ symmetry of the room-temperature phase but show that the transition involves a complex interplay of six different normal modes belonging to four different irreducible representations. Three of them are necessary for the observed symmetry break. We do not find any feature in the energy landscape that would force the simultaneous condensation of these three order parameters and cause such an avalanche transition, so we suggest that further experimental work might be able to detect intermediate phases. On the other hand, the necessary condensation of pairs of normal modes of the same symmetry already puts Bi 4 Ti 3 O 12 outside the standard soft-mode paradigm and has important structural implications. In particular, the approximate rigidity of the BiO 6 octahedra is due to anharmonic couplings of these modes. In addition, a comparison of the energy calculations and the behavior of the bond-valence global instability index is presented.

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Bonding at Oxide Surfaces

Enterkin

Poeppelmeier

2014

Structure and Bonding

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Comparison of empirical bond-valence and first-principles energy calculations for a complex structural instability

Cited by 27 publications

References 23 publications

Distortion modes and related ferroic properties of the stuffed tridymite-type compoundsSrAl2O4andBaAl2
Perez-Mato
¹
,
Withers
²
,
Larsson
³

et al. 2009
Phys. Rev. B
Self Cite
37
3
19
0
View full text Add to dashboard Cite

Distortion modes and related ferroic properties of the stuffed tridymite-type compoundsSrAl2O4andBaAl2
Perez-Mato
¹
,
Withers
²
,
Larsson
³

et al. 2009
Phys. Rev. B
Self Cite
37
3
19
0
View full text Add to dashboard Cite

Multiple instabilities inBi4Ti3O12: A ferroelectric beyond the soft-mode paradigm

Bonding at Oxide Surfaces

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Comparison of empirical bond-valence and first-principles energy calculations for a complex structural instability

Cited by 27 publications

References 23 publications

Distortion modes and related ferroic properties of the stuffed tridymite-type compoundsSrAl2O4andBaAl2Perez-Mato1, Withers2, Larsson3 et al. 2009Phys. Rev. BSelf Cite373190View full textAdd to dashboardCite

Distortion modes and related ferroic properties of the stuffed tridymite-type compoundsSrAl2O4andBaAl2Perez-Mato1, Withers2, Larsson3 et al. 2009Phys. Rev. BSelf Cite373190View full textAdd to dashboardCite

Multiple instabilities inBi4Ti3O12: A ferroelectric beyond the soft-mode paradigm

Bonding at Oxide Surfaces

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Distortion modes and related ferroic properties of the stuffed tridymite-type compoundsSrAl2O4andBaAl2
Perez-Mato
¹
,
Withers
²
,
Larsson
³

et al. 2009
Phys. Rev. B
Self Cite
37
3
19
0
View full text Add to dashboard Cite

Distortion modes and related ferroic properties of the stuffed tridymite-type compoundsSrAl2O4andBaAl2
Perez-Mato
¹
,
Withers
²
,
Larsson
³

et al. 2009
Phys. Rev. B
Self Cite
37
3
19
0
View full text Add to dashboard Cite