Why Are the Conventionally-Assumed High-Pressure Crystal Structures of Ordinary Semiconductors Unstable?

Zunger, Alex; Kim, K.; Ozoliņš, Vidvuds

doi:10.1002/1521-3951(200101)223:2<369::aid-pssb369>3.0.co;2-6

Cited by 19 publications

(7 citation statements)

References 39 publications

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“…74 Measurements of the phonon-dispersion relations under pressure performed recently 76 on PbTe have yielded a very small but negative value of ␥ TA for the X point, contrary to our calculations for ZnO. In contrast to calculations reported for GaP, 77 the rocksalt structure of ZnO exhibits a very small but positive Grüneisen parameter for the TA͑X͒ mode, as shown in Table VIII. This behavior may be related to the nonmetallic nature of the rocksalt modification of ZnO, which is deduced indirectly from the nonzero LO-TO splitting at the ⌫ point and has been recently observed in measurements of the optical absorption, and also obtained in ab initio calculations.…”

Section: Zinc Blende and Rocksaltcontrasting

confidence: 96%

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Pressure dependence of the lattice dynamics of ZnO: Anab initioapproach

et al. 2004

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We have performed first-principles calculations of the electronic structure of ZnO, and applied them to the determination of structural and lattice-dynamical properties and their dependence on pressure. The dynamical matrices have been obtained for the wurtzite, zinc-blende, and rocksalt modifications with several lattice parameters optimized for pressures up to 12 GPa. These matrices are employed to calculate the one-phonon densities of states ͑DOS͒ and the two-phonon DOS associated with either sums or differences of phonons. These results provide the essential tools to analyze the effect of isotope-induced mass disorder and anharmonicity on phonon linewidths, which we discuss here and compare with experimental data from Raman spectroscopy, including first-and second-order spectra. Agreement of calculated properties with experimental results improves considerably when the renormalization due to anharmonicity is subtracted from the experimental data.

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Section: Zinc Blende and Rocksaltcontrasting

confidence: 96%

“…78 GaP seems to be metallic in the rocksalt structure. 77 According to Table IV, the calculated values of ‫ץ‬Z*/‫ץ‬p are rather similar for the three ZnO modifications. This derivative can be related to the derivative of an effective charge with respect to the bond length.…”

Section: Zinc Blende and Rocksaltmentioning

confidence: 71%

Pressure dependence of the lattice dynamics of ZnO: Anab initioapproach

et al. 2004

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“…36 We have investigated phonon modes at ⌫ point with a force-constant matrix diagonalization method, implemented in VASP, using the MS2 structure with a convenient hexagonal unit cell. MS2-LiB has two weakly interacting boron layers per unit cell which leads to an effective double degeneracy of the known phonon modes at ⌫ in the AlB 2 -type compounds.…”

Section: -2mentioning

confidence: 99%

“…Ab initio studies have shown that existence of energetically favorable phases could be barred by dynamical instabilities [36]. We have investigated phonon modes at Γ-point with a force-constant matrix diagonalization method, implemented in VASP, using the MS2 structure with a convenient rhombohedral unit cell.…”

mentioning

confidence: 99%

Prediction of different crystal structure phases in metal borides: A lithium monoboride analog toMgB2

Kolmogorov

Curtarolo

2006

Phys. Rev. B

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Modern compound prediction methods can efficiently screen large numbers of crystal structure phases and direct the experimental search for new materials. One of the most challenging problems in alloy theory is the identification of stable phases with a never seen prototype; such predictions do not always follow rational strategies. While performing ab initio data mining of intermetallic compounds we made an unexpected discovery: even in such a well-studied class of systems as metal borides there are previously unknown layered phases comparable in energy to the existing ones. With ab initio calculations we show that the new metalsandwich ͑MS͒ lithium monoboride phases are marginally stable under ambient conditions but become favored over the known stoichiometric compounds under moderate pressures. The MS lithium monoboride exhibits electronic features similar to those in magnesium diboride and is expected to be a good superconductor.Development of theoretical methods able to guide the experimental search for new materials with desired properties is a fast-growing field of research in materials science. 1-8 A particular effort has been put into the coupling of ab initio electronic structure methods with efficient data-mining algorithms to determine and utilize correlations in binding mechanisms in a chosen set of structures. 4-7 However, even with the most advanced optimization algorithms one has to restrict the search space to a given structure, 4 lattice type, 5 or prototype library. 6,7 Moreover, in some approaches structures are kept symmetry constrained or not relaxed at all. Considering the rich nature of bonding in solids, such limitations can lead to overlooking the most stable phases. This makes the identification of new prototypes a vital step towards a more complete description of alloys.Expanding the library of ab initio energies of binary alloys described in Ref. 6 we observed that one of the phases in the Mg-B system, A 2 B 2 fcc-͑111͒ ͓or V2 ͑Ref. 9͔͒, unexpectedly underwent significant structural relaxation and became comparable in energy to the mixture of two coexisting stable phases, MgB 2 and hcp-Mg. Upon examination of the relaxation process we found that there is a continuous symmetry conserving path from V2 ͓Fig. 1͑c͔͒ to a new metalsandwich ͑MS͒ structure MS1 ͓Fig. 1͑b͔͒. 10 The latter has four atoms per unit cell with hexagonal layers of boron separated by two triangular layers of metal; it bears a strong resemblance to the AlB 2 prototype ͓Fig. 1͑a͔͒ having a similar sp 2 boron-boron bonding. The extra metal layer is inserted in a close-packed fashion with the Mg-Mg bond length close to that in the pure hcp structure, which may account for the near stability ͑by a few meV/atom͒ of the magnesium monoboride. To the best of our knowledge, this structure has not been considered before for any binary alloy. We have constructed a series of related MS structures with different stacking sequences of metal and boron layers ͓such as MS2 in Fig. 1͑d͒ ͑Ref. 11͔͒, which is a generalization of the MS1 pr...

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“…e.g. Dmitriev et al, 1988;Christy, 1993;O'Keeffe & Hyde, 1996;Zunger et al, 2001). Even phase transitions usually termed`reconstructive' may be regarded in an analogous way if the intermediate structure can be obtained by a step-by-step symmetry reduction leading to a sequence of subgroups of the space groups of both phases.…”

Section: Introductionmentioning

confidence: 99%

Relations between the zinc-blende and the NaCl structure type

Sowa¹

2003

Acta Cryst Sect A

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A new model for the transformation from the zinc-blende to the NaCl type is developed on the basis of the deformation of a 4-connected heterogeneous sphere packing in space group P3(2). The geometrical features of this transition are discussed by investigating the analogous deformations of a 4-connected homogeneous sphere packing in the supergroup P3(2)21 of P3(2). In this space group, the atomic arrangement corresponds to a diamond configuration. During the phase transition, it is deformed under preservation of all sphere contacts until a cubic primitive lattice is reached, the analogue of the NaCl arrangement formed by like atoms. The intermediate structure that occurs between the zinc-blende and the NaCl type is compared with the cinnabar type.

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Why Are the Conventionally-Assumed High-Pressure Crystal Structures of Ordinary Semiconductors Unstable?

Cited by 19 publications

References 39 publications

Pressure dependence of the lattice dynamics of ZnO: Anab initioapproach

Pressure dependence of the lattice dynamics of ZnO: Anab initioapproach

Prediction of different crystal structure phases in metal borides: A lithium monoboride analog toMgB2

Relations between the zinc-blende and the NaCl structure type

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