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Pressure Effects on Structural, Electronic, Elastic, and Optical Properties of Cubic and Tetragonal Phases of BaZrO_{3}

100%

Yang X., Wang Y., Song Q., Chen Y., Hong Xue Y.

Acta Physica Polonica A

2018

vol. 133

issue 5

1138-1143

A recent experimental study found the phase transition from cubic to tetragonal phase at 17.2 GPa in BaZrO_{3}. In this paper, we investigate the structural, electronic, elastic, and optical properties of BaZrO_{3} in the cubic and tetragonal structures under pressure by using first-principle density-functional theory. The main results are summarized as follows: (1) An indirect band structure is displayed for both cubic and tetragonal phases. The band gap increases by ~1 eV as a result of the phase transition. (2) The elastic constants C_{ij}'s indicate that the cubic and tetragonal phases are mechanically stable. The easiest deformation mechanism in both phases is the shear along the (100) plane. (3) The real and imaginary parts of dielectric function for the cubic and tetragonal phases shift towards higher energies with pressure. Our results are in agreement with the available experimental and prior theoretical data.

Structural, electronic and elastic properties of Ti2TlC, Zr2TlC and Hf2TlC

88%

Bouhemadou A.

Using First-principle calculations, we have studied the structural, electronic and elastic properties of M2TlC, with M = Ti, Zr and Hf. Geometrical optimization of the unit cell is in good agreement with the available experimental data. The effect of high pressures, up to 20 GPa, on the lattice constants shows that the contractions are higher along the c-axis than along the a axis. We have observed a quadratic dependence of the lattice parameters versus the applied pressure. The band structures show that all three materials are electrical conductors. The analysis of the site and momentum projected densities shows that bonding is due to M d-C p and M d-Tl p hybridizations. The M d-C p bonds are lower in energy and stiffer than M d-Tl p bonds. The elastic constants are calculated using the static finite strain technique. We derived the bulk and shear moduli, Young’s modulus and Poisson’s ratio for ideal polycrystalline M2TlC aggregates. We estimated the Debye temperature of M2TlC from the average sound velocity. This is the first quantitative theoretical prediction of the elastic properties of Ti2TlC, Zr2TlC, and Hf2TlC compounds that requires experimental confirmation.

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1 Acta Physica Polonica A

1 Open Physics

1 2018

1 2009

1 Bouhemadou A.

1 Chen Y.

1 Hong Xue Y.

1 Song Q.

1 Wang Y.

1 Yang X.

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Pressure Effects on Structural, Electronic, Elastic, and Optical Properties of Cubic and Tetragonal Phases of BaZrO_{3}

Structural, electronic and elastic properties of Ti2TlC, Zr2TlC and Hf2TlC