Lattice dynamics of CuAlO₂ under high pressure from ab initio calculations

Abstract

The density functional perturbation theory is employed to study the vibrational properties of CuAlO 2 under pressure. The calculations are preformed using the pseudopotential wave method and the local density approximation for the exchange-correlation (XC) potential. The d electrons of Cu are treated as valence states. We present the phonon dispersion curves. Our results are in good agreement with the available experimental Raman scattering experiments. Ab initio calculations show the presence of a dynamical instability, possibly related with the experimentally observed phase transition.

Density functional theory study of 3R– and 2H–CuAlO2 in tensile stress

“…The lattice parameters a and c are about 2.8813 and 17.1006Ǻ for 3R-CuAlO 2 , 2.8809 and 11.4023Ǻ for 2H-CuAlO 2 , respectively, which are consistent with the experimental data of 3R-CuAlO 2 [15,21,22] and 2H-CuAlO 2 [21,33] and other theoretical results of 3R-CuAlO 2 [9,18,21,28] and 2H-CuAlO 2 [18,21]. We can see that the selection of the plane-wave ultrasoft pseudopotential is reasonable.…”

“…However, great interest in the high-pressure phases of this compound has been motivated [26][27][28][29][30] not only to clarify its phase diagram but also to learn about the evaluation of the delafossite-type AMO 2 oxides at high pressure. There is a reversible phase transition of 3R-CuAlO 2 at 34 ± 2 GPa by means of Raman scattering [26], but the density functional perturbation theory (DFPT)-LDA calculation shows the dynamical instability of 3R-CuAlO 2 at 45 GPa [28] due to the anharmonic effects when soft modes are presented. Recently the discovery [30] of phase transition pressure between 3R and 2H is 15.4 GPa, and the independent elastic constants of 3R-and 2H-CuAlO 2 show the presences of mechanical instability at 26.2 and 27.8 GPa, respectively.…”

The use of strain and grain boundaries to tailor phonon transport properties: A first-principles study of 2H-phase CuAlO2. II

“…The atomic positions were then allowed to relax keeping the volume of the cell constant. Imparting confidence in this particular methodology, the lattice parameters under these hydrostatic strains are found to be consistent with theory and experimental values [73], [74]. Figure 5(a) is a plot of the thermal conductivity vs. strain for both a structure without grains (blue circles) and for one with 3 nm grains (red stars).…”

Structural stability of high-pressure phase in the immiscible Cu–Nb system studied by lattice dynamics calculation

“…In some occasion, the imaginary phonon may appear or disappear when the pressure is elevated. For example, Rodríguez-Hernández et al [8] reported that in their calculation about CuAlO 2 , imaginary phonons appeared at 45 GPa, which is of agreement with the experimental finding that a reversible phase transition around 36 GPa could happen. Kong et al [9] reported that the imaginary phonons of hypothetical L1 2 -, D0 3 -, and D0 19 -Cu 3 Ta disappeared at 2.7, 11.8 and 14.7 GPa, respectively.…”