Effects of epitaxial strains on spontaneous polarizations and band gaps of alkaline-earth-metal oxides MO (M = Mg, Ca, Sr, Ba)

Characterization of Electronic Properties, Exchange Splitting and Ferromagnetic Arrangement in New Ti-Doped BaO

“…Moreover, the results of the lattice constant and bulk modulus of BaO are in good concordance with the experimental values [26][27][28] and theoretical calculations [16] found by GGA-WC [21]. Also, these parameters are better than the theoretical values [11,16,[30][31][32] calculated with generalised gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE) [33] and the local density approximation (LDA) [34] with respect to the experimental values, meaning that the GGA-WC [21] provides good results for the structural parameters. The performance of GGA-WC potential compared to other approximations for determining structural properties results from the fourth order of expansion of its gradient of exchange and correlation functional [21,[35][36][37].…”

“…The Ba0.875Ti0.125O has direct HMF gap of 2.701 eV situated at the  high symmetry point and its HM gap is 0.803 eV located between the valence band maximum and Fermi level. The wide gap of BaO of 3.5 calculated with the TB-mBJ is more improved with respect to the theoretical values [11,16,30,38,39] found by the GGA-WC [21], GGA-PBE [33] and LDA [34] approximations. The better gap of BaO is due to the performance of TB-mBJ semi-local exchange correlation potential for predicting band gaps of semiconductors and insulators [23,43,44].…”

“…The structural properties such as the lattice constants (a), bulk modules (B) and their pressure derivatives (B') of BaO and Ba0.785Ti0.125O compounds have calculated by fitting the empirical Murnaghan's equation of state [25]. The obtained results are given in Table 1 with other experimental data [26][27][28][29] and theoretical values [11,16,[30][31][32]. We have noticed that there are changes in the structural parameters (a) and (B) of Ba0.875Ti0.125O doping material compared to the BaO.…”

“…The performance of GGA-WC potential compared to other approximations for determining structural properties results from the fourth order of expansion of its gradient of exchange and correlation functional [21,[35][36][37]. Table 2 summarise the values of direct band gap E XX of BaO, HMF gap GHMF and HM gap GHM of minority-spin bands of Ba0.875Ti0.125O with other theoretical [11,16,30,38,39] and experimental [40][41][42] values. The Ba0.875Ti0.125O has direct HMF gap of 2.701 eV situated at the  high symmetry point and its HM gap is 0.803 eV located between the valence band maximum and Fermi level.…”

“…The barium oxide (BaO) is one of the alkaline-earth-metal binary oxides; it has wide band gap owing to its high ionicity [11]. This compound has several technological applications for example it is used as a buffer layer in the epitaxial growth of multifunctional perovskite oxides directly on silicon [11,12]. The alkaline-earth-metal binary oxides have been considered as potential materials for spintronics and optoelectronics applications [13][14][15].…”