Local structural aspects of the orthorhombic to pseudo-cubic phase transformation in

Božin, Emil S.; Qiu, X.; Schmidt, M.; Paglia, Gianluca; Mitchell, J. F.; Radaelli, P. G.; Proffen, Thomas; Billinge, Simon J. L.

doi:10.1016/j.physb.2006.05.137

Cited by 10 publications

(9 citation statements)

References 10 publications

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“…The same study suggested that the ground-state-like orbital order remains within clusters ~16 Å in diameter above the T JT . The nature of the O-O' transition appears to have the same origin when the phase line is crossed both vs temperature at fixed doping, and vs doping at fixed temperature [18]. Here we extend these results to the case when the phase line is crossed as a function of doping at 550 K temperature, deep in the insulating phase.…”

Section: Introductionsupporting

confidence: 59%

“…It has been demonstrated that this effect is related to the rearrangements within the oxygen sublattice [18]. Quantification of these observations, by fitting the PDF profiles over relatively narrow r-range, further showed that the local JT distortion remains unchanged across the Jahn-Teller transition, while the features sensitive to oxygen rotations that correspond to furtherneighbour correlations change dramatically and vanish in the pseudo-cubic phase [18]. Note that there is a systematic gradual shift of the intensity of the 2.17 Å long bond peak towards lower r-values.…”

Section: Resultsmentioning

confidence: 99%

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Utilizing total scattering to study the Jahn-Teller transition in La_1-xCa_xMnO₃

Božin¹,

Qiu²,

Worhatch³

et al. 2007

Z. Kristallogr. Suppl.

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Total scattering based atomic pair distribution function (PDF) analysis, with the advent of high data throughput neutron powder diffractometers, helps understanding the nature of the Jahn-Teller (JT) phase transition in La 1-x Ca x MnO 3 colossal magnetoresistive (CMR) manganites. The JT distortion of the MnO 6 octahedra, is long-range ordered in the orthorhombic (O) phase, but disappears in the pseudo-cubic (O') phase crystallographically. An anomalous unit cell volume contraction occurs at the transition. The PDF study indicates that the distortion persists locally deep in the O' phase, contrary to the crystallographic view. Simultaneously, local structural features observed in PDF at 10.3 Å, sensitive to the oxygen sublattice changes, evolve dramatically across the transition. The same effect is observed irrespective of the way the O-O' phase boundary is crossed: it is seen both in the temperature series data for x=0, and in the doping series data at 310 K and at 550 K.

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Section: Introductionsupporting

confidence: 59%

Section: Resultsmentioning

confidence: 99%

Utilizing total scattering to study the Jahn-Teller transition in La_1-xCa_xMnO₃

Božin¹,

Qiu²,

Worhatch³

et al. 2007

Z. Kristallogr. Suppl.

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“…The mechanism for this almost certainly involves the development of local distortions or strain heterogeneities when differently sized cations occupy adjacent crystallographic sites in a disordered manner, and a similar mechanism can be envisaged for LaMnO 3 . Sá nchez et al 2003, Qiu et al (2005) and Bozin et al (2006) seem to have shown definitively that individual MnO 6 octahedra in LaMnO 3 retain a degree of Jahn-Teller distortion up to high temperatures. The Pnma (tilted) $ Pnma (tilted + JT) transition at $ 750 K is effectively then due to a change from ordered to disordered arrangements of the octahedra, with any ordering of the orientations above 750 K occurring only within clusters up to $ 16 Å in diameter (Sá nchez et al 2003;Qiu et al 2005).…”

Section: Strain Analysis Of Lamnomentioning

confidence: 95%

Symmetry rules and strain/order-parameter relationships for coupling between octahedral tilting and cooperative Jahn–Teller transitions in ABX ₃ perovskites. II. Application

Carpenter

Howard

2009

Acta Crystallogr Sect B

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The structural evolution of selected perovskites containing Jahn-Teller cations has been investigated in the light of a formal analysis of symmetry hierarchies for phase transitions driven by octahedral tilting and Jahn-Teller cooperative distortions. General expressions derived from the strain/order-parameter coupling relationships allowed by symmetry are combined with observed changes in lattice parameters to reveal details of order-parameter evolution and coupling. LuVO3, YbVO3, YVO3 and CeVO3 are representative of systems which develop Jahn-Teller ordering schemes associated with irreducible representations M2+ and R3+ of the space group Pm3m. Tilting of their octahedra is associated with M3+ and R4+. The Pnma (M3+ + R4+ tilting) <--> P2(1)/a (M3+ + R4+ tilting, R3+ Jahn-Teller order) transition below room temperature is close to second order in character. Shear strains which depend primarily on tilt angles show little variation, implying that there is only weak coupling between the tilting and Jahn-Teller order parameters. The subsequent P2(1)/a <--> Pnma (M3+ + R4+ tilting, M2+ Jahn-Teller order) is first order in character, and involves either a reduction in the R4+ tilt angle or a change in the strength of tilt/Jahn-Teller order-parameter coupling. In LaMnO3, the isosymmetric Pnma (M3+ + R4+ tilting) <--> Pnma (M3+ + R4+ tilting, M2+ Jahn-Teller order) transition can be described in terms of a classical first-order transition conforming to a 246 Landau expansion with negative fourth-order coefficients. Strain evolution in Ba-doped samples suggests that the transition becomes second order in character and reveals a new strain relaxation mechanism in LaMnO3 which might be understood in terms of local strain heterogeneities due to the disordering of distorted MnO6 octahedra. Transitions in PrAlO3 and La(0.5)Ba(0.5)CoO3 illustrate the transformation behaviour of systems in which the Jahn-Teller ordering scheme is associated with the irreducible representation Gamma3+. Overall, coupled tilting + Jahn-Teller phase transitions in perovskites conform to mean-field behaviour, consistent with the underlying role of strain in promoting long interaction lengths.

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“…Local structural distortions arising from atomic displacements from their high symmetry positions are known to influence catalytic properties 12 and are relevant to properties near phase transformation. 13,14 They influence electronic, 14,15 dielectric, 16 and ferroelectric properties 17 of a variety of oxides. A clear picture about the tendency of a structure to undergo local distortions is obtained from the knowledge of unstable phonons in full phonon dispersion of a material.…”

Section: Introductionmentioning

confidence: 99%

Structure of Ce1−xSnxO2 and its relation to oxygen storage property from first-principles analysis

Gupta

Kumar²,

Hegde³

et al. 2010

The Journal of Chemical Physics

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CeO(2)-SnO(2) solid solution has been reported to possess high oxygen storage/release property which possibly originates from local structural distortion. We have performed first-principles based density functional calculations of Ce(1-x)Sn(x)O(2) structure (x=0, 0.25, 0.5, 1) to understand its structural stability in fluorite in comparison to rutile structure of the other end-member SnO(2), and studied the local structural distortion induced by the dopant Sn ion. Analysis of relative energies of fluorite and rutile phases of CeO(2), SnO(2), and Ce(1-x)Sn(x)O(2) indicates that fluorite structure is the most stable for Ce(1-x)Sn(x)O(2) solid solution. An analysis of local structural distortions reflected in phonon dispersion show that SnO(2) in fluorite structure is highly unstable while CeO(2) in rutile structure is only weakly unstable. Thus, Sn in Ce(1-x)Sn(x)O(2)-fluorite structure is associated with high local structural distortion whereas Ce in Ce(1-x)Sn(x)O(2)-rutile structure, if formed, will show only marginal local distortion. Determination of M-O (M=Ce or Sn) bond lengths and analysis of Born effective charges for the optimized structure of Ce(1-x)Sn(x)O(2) show that local coordination of these cations changes from ideal eightfold coordination expected of fluorite lattice to 4+4 coordination, leading to generation of long and short Ce-O and Sn-O bonds in the doped structure. Bond valence analyses for all ions show the presence of oxygen with bond valence approximately 1.84. These weakly bonded oxygen ions are relevant for enhanced oxygen storage/release properties observed in Ce(1-x)Sn(x)O(2) solid solution.

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Local structural aspects of the orthorhombic to pseudo-cubic phase transformation in

Cited by 10 publications

References 10 publications

Utilizing total scattering to study the Jahn-Teller transition in La_1-xCa_xMnO₃

Utilizing total scattering to study the Jahn-Teller transition in La_1-xCa_xMnO₃

Symmetry rules and strain/order-parameter relationships for coupling between octahedral tilting and cooperative Jahn–Teller transitions in ABX ₃ perovskites. II. Application

Structure of Ce1−xSnxO2 and its relation to oxygen storage property from first-principles analysis

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Local structural aspects of the orthorhombic to pseudo-cubic phase transformation in

Cited by 10 publications

References 10 publications

Utilizing total scattering to study the Jahn-Teller transition in La1-xCaxMnO3

Utilizing total scattering to study the Jahn-Teller transition in La1-xCaxMnO3

Symmetry rules and strain/order-parameter relationships for coupling between octahedral tilting and cooperative Jahn–Teller transitions in ABX 3 perovskites. II. Application

Structure of Ce1−xSnxO2 and its relation to oxygen storage property from first-principles analysis

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Utilizing total scattering to study the Jahn-Teller transition in La_1-xCa_xMnO₃

Utilizing total scattering to study the Jahn-Teller transition in La_1-xCa_xMnO₃

Symmetry rules and strain/order-parameter relationships for coupling between octahedral tilting and cooperative Jahn–Teller transitions in ABX ₃ perovskites. II. Application