LDA and GGA calculations for high-pressure phase transitions in ZnO and MgO

Jaffe, John E.; Snyder, James A.; Lin, Zijing; Hess, Aaron

doi:10.1103/physrevb.62.1660

Cited by 427 publications

(222 citation statements)

References 34 publications

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“…The transformation pressure observed here is consistent with experimental measurements in the range of 8.7-9.1 GPa (Desgreniers, 1998;Karzel et al, 1996). These values are higher than the phase equilibrium stress predicted by first-principles calculations (6.6-8.5 GPa) (Jaffe and Hess, 1993;Jaffe et al, 2000;Limpijumnong and Jungthawan, 2004). The difference is that, while the MD and experimental values are actual transformation stresses which reflect the effect of the energy barrier between the WZ and RS phases, the DFT phase equilibrium stress only indicates the level of stress at which the two phases are equally favored but does not relate to the stress required to overcome the energy barrier and activate the transformation.…”

Section: Uniaxial Tension Along the ½01 10 Orientationsupporting

confidence: 72%

Effect of load triaxiality on polymorphic transitions in zinc oxide

Kulkarni

Sarasamak

Wang

et al. 2008

Mechanics Research Communications

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Molecular dynamics (MD) simulations and first-principles calculations are carried out to analyze the stability of both newly discovered and previously known phases of ZnO under loading of various triaxialities. The analysis focuses on a graphite-like phase (HX) and a body-centered-tetragonal phase (BCT-4) that were observed recently in ½0 1 1 0 -and [0 0 0 1]-oriented nanowires respectively under uniaxial tensile loading as well as the natural state of wurtzite (WZ) and the rocksalt (RS) phase which exists under hydrostatic pressure loading. Equilibrium critical stresses for the transformations are obtained. The WZ ! HX transformation is found to be energetically favorable above a critical tensile stress of 10 GPa in ½01 10 nanowires. The BCT-4 phase can be stabilized at tensile stresses above 7 GPa in [0 0 0 1] nanowires. The RS phase is stable at hydrostatic pressures above 8.2 GPa. The identification and characterization of these phase transformations reveal a more extensive polymorphism of ZnO than previously known. A crystalline structure-load triaxiality map is developed to summarize the new understanding.

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Section: Uniaxial Tension Along the ½01 10 Orientationsupporting

confidence: 72%

Effect of load triaxiality on polymorphic transitions in zinc oxide

Kulkarni

Sarasamak

Wang

et al. 2008

Mechanics Research Communications

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“…Among them are Refs. 26,27,28,29,30,31,32,33,34,35,36, using a variety of ab initio computational methods. There are, however, not many studies of Mg x Zn 1−x O alloys, possibly due to the complex interplay of their electronic and geometric structures.…”

Section: Introductionmentioning

confidence: 99%

Structural phase transitions and fundamental band gaps ofMgxZn1−xOalloys from first principles

et al. 2009

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The structural phase transitions and the fundamental band gaps of MgxZn1−xO alloys are investigated by detailed first-principles calculations in the entire range of Mg concentrations x, applying a multiple-scattering theoretical approach (Korringa-Kohn-Rostoker method). Disordered alloys are treated within the coherent potential approximation (CPA). The calculations for various crystal phases have given rise to a phase diagram in good agreement with experiments and other theoretical approaches. The phase transition from the wurtzite to the rock-salt structure is predicted at the Mg concentration of x = 0.33, which is close to the experimental value of 0.33 − 0.40. The size of the fundamental band gap, typically underestimated by the local density approximation, is considerably improved by the self-interaction correction. The increase of the gap upon alloying ZnO with Mg corroborates experimental trends. Our findings are relevant for applications in optical, electrical, and in particular in magnetoelectric devices.

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“…Neither the use of the generalized-gradient approximation (GGA) nor the inclusion of SO coupling into the calculations seems able to remedy the above shortcomings. 15,17,26 The effective masses of the charge carriers are more indefinite parameters for the zinc monochalcogenides. Owing to low crystal quality only a few cyclotron resonance experiments have been performed for ZnO, 27,28 ZnS, 29,30 and ZnTe.…”

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confidence: 99%

Coulomb correlation effects in zinc monochalcogenides

Karazhanov

Ravindran

Großner

et al. 2006

Journal of Applied Physics

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Electronic structure and band characteristics for zinc monochalcogenides with zinc-blende-and wurtzite-type structures are studied by first-principles density-functional-theory calculations with different approximations. It is shown that the local-density approximation underestimates the band gap and energy splitting between the states at the top of the valence band, misplaces the energy levels of the Zn-3d states, and overestimates the crystal-field-splitting energy. The spin-orbit-coupling energy is found to be overestimated for both variants of ZnO, underestimated for ZnS with wurtzitetype structure, and more or less correct for ZnSe and ZnTe with zinc-blende-type structure. The order of the states at the top of the valence band is found to be anomalous for both variants of ZnO, but is normal for the other zinc monochalcogenides considered. It is shown that the Zn-3d electrons and their interference with the O-2p electrons are responsible for the anomalous order. The effective masses of the electrons at the conduction-band minimum and of the holes at the valence-band maximum have been calculated and show that the holes are much heavier than the conduction-band electrons in agreement with experimental findings. The calculations, moreover, indicate that the effective masses of the holes are much more anisotropic than the electrons. The typical errors in the calculated band gaps and related parameters for ZnO originate from strong Coulomb correlations, which are found to be highly significant for this compound. The local-density-approximation with multiorbital mean-field Hubbard potential approach is found to correct the strong correlation of the Zn-3d electrons, and thus to improve the agreement between the experimentally established location of the Zn-3d levels and that derived from pure LDA calculations.

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LDA and GGA calculations for high-pressure phase transitions in ZnO and MgO

Cited by 427 publications

References 34 publications

Effect of load triaxiality on polymorphic transitions in zinc oxide

Effect of load triaxiality on polymorphic transitions in zinc oxide

Structural phase transitions and fundamental band gaps ofMgxZn1−xOalloys from first principles

Coulomb correlation effects in zinc monochalcogenides

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