Alkaline-Earth Metal Effects on Physical Properties of Ferromagnetic AVO3 (A = Ba, Sr, Ca, and Mg): Density Functional Theory Insights

Abstract

The effects of alkaline-earth metals on electronic, optical, thermodynamic, and physical properties of ferromagnetic AVO₃ (A = Ba, Sr, Ca, and Mg) have been investigated by first-principles calculations within the GGA+U formalism based on density functional theory. The optimized structural parameters are in good agreement with the available experimental results that evaluate the reliability of our calculations. The cell and mechanical stability is discussed using the formation energy and Born stability criteria, respectively. The mechanical behaviors of AVO₃ are discussed on the basis of the results of elastic constants, elastic moduli, Peierls stress, and Vickers hardness. The nature of the ductile-brittle transition of AVO₃ compounds was confirmed by the values of Pugh's ratio, Poisson's ratio, and Cauchy pressure. The electronic band structures, as well as density of states, reveal the half-metallic behavior of BaVO₃ and SrVO₃. However, CaVO₃ and MgVO₃ exhibit spin-gapless and magnetic semiconductor characteristics, respectively. The microscopic origin of the transition from the half-metallic to semiconductor nature of AVO₃ is rationalized using electronic properties. The presence of covalent, ionic, and metallic bonds in AVO₃ compounds is found by the analysis of bonding properties. The single-band nature of half-metallic AVO₃ is seen by observing hole-like Fermi surfaces in this study. Furthermore, the various thermodynamic and optical properties are calculated and analyzed. The refractive index suggests that AVO₃ could be a potential candidate for applications to high-density optical data storage devices.

Figure 1

(Color online) Unit cell of cubic perovskite AVO₃ (A = Ba, Sr, Ca, and Mg).

Figure 2

(Color online) Calculated Pugh’s ratio (G/B), Poisson’s ratio (ν), and Cauchy pressure (C₁₂–C₄₄) showing the graphical representation of ductile/brittle behavior of AVO₃ (A = Ba, Sr, Ca, and Mg). The horizontal dashed lines indicate the ductile–brittle transition line.

Figure 3

(Color online) Isotropic/anisotropic nature of AVO₃ shown graphically by Zener’s anisotropy index (A_G) and the universal (A^U) anisotropy index, where the dash-dotted lines denote the isotropic line.

Figure 4

(Color online) Directional dependences of the shear modulus, G (upper curves), Young’s modulus, E (middle curves), and Poisson’s ratio, ν (lower curves), of AVO₃ (A = Ba, Sr, Ca, and Mg).

Figure 5

(Color online) Spin-polarized GGA+U (U = 2.5 eV for V 3d) calculated electronic band structures of (a) BaVO₃, (b) SrVO₃, (c) CaVO₃, and (d) MgVO₃ along the high-symmetry directions in the Brillouin zone.

Figure 6

(Color online) Total and partial density of states of (a) BaVO₃, (b) SrVO₃, (c) CaVO₃, and (d) MgVO₃ with the spin-polarized GGA+U (U = 2.5 eV for V 3d) method.

Figure 7

(Color online) (a–d) Total density of states (TDOS) and partial density of states (PDOS) at the Fermi level (E_F) of AVO₃. (e) Band gap energy (E_g) of AVO₃ in the spin-down channel.

Figure 8

(Color online) Electronic charge density of (upper left) BaVO₃, (upper right) SrVO₃, (lower left) CaVO₃, and (lower right) MgVO₃.

Figure 9

(Color online) Fermi surface topology of (a) BaVO₃, (b) SrVO₃, and (c) CaVO₃.

Figure 10

(Color online) Energy-dependent dielectric function (real part, ε₁, and imaginary part, ε₂) of AVO₃ compounds.

Figure 11

(Color online) Refractive index (n) and extinction coefficient (k) of AVO₃ compounds as a function of energy.

Figure 12

(Color online) Real parts of conductivity (σ) and absorption coefficient (α) of AVO₃ compounds as a function of energy.

Figure 13

(Color online) Energy-dependent reflectivity (R) and loss function (L) of the AVO₃ compounds.