Structural, Electronic, Elastic, and Optical Properties of Cubic BaLiX₃ (X = F, Cl, Br, or I) Perovskites: An <i>Ab-initio</i> DFT Study

Abstract

This study reports for the first time the theoretical prediction of structural, electronic, elastic and optical properties of cubic BaLiCl3, BaLiBr3, and BaLiI3 perovskites. The corresponding properties of the well-known BaLiF3 are also theoretically investigated. Density Functional Theory (DFT) using the Generalized Gradient Approximation (GGA) was implemented within the Quantum Espresso package to investigate the properties of the perovskites. The results revealed that BaLiX3 (X = F, Cl, Br, and I) are in ionic crystal forms with optimized lattice parameters of 4.04, 4.90, 5.21, and 5.66 Å, respectively. The minor band gaps were found to be 6.62 eV (Γ→Γ), 4.29 eV (R→Γ), 3.50 eV (R→Γ), and 2.58 eV (R→Γ) for the respective compounds. The investigation of their elastic properties indicated that these perovskites are all mechanically stable, while only BaLiBr3 and BaLiI3 are malleable. Finally, the studied perovskites exhibit excellent optical properties, including low reflectivity and high absorption in the ultraviolet region. Hence, it is predicted that these perovskites are suitable for various optoelectronic applications involving absorption in the UV region. However, BaLiBr3 and BaLiI3 are more favorable than BaLiF3 and BaLiCl3 to be deposited as thin films due to their flexibility.

A DFT investigation of lead-free TlSnX3 (X = Cl, Br, or I) perovskites for potential applications in solar cells and thermoelectric devices

“…This observation is consistent with the ndings of a recent study on isoelectronic compounds like InSnX 3 (X = Cl, Br, I) perovskites. 18 This also corresponds with similar trends reported for a wide range of ABX 3 perovskites [35][36][37][38][39][40][41] and double perovskites. [42][43][44][45][46][47][48][49] Another important parameter is the formation energy of these compounds, which is closely related to their chemical stability.…”

Lead-free perovskites InSnX3(X = Cl, Br, I) for solar cell applications: a DFT study on the mechanical, optoelectronic, and thermoelectric properties

“…Figures 6(a)-(c) (right) also illustrate that the covalent character of the Sn-X bonds is quite strong as seen by some accumulation of electrons between Sn and X atoms and by nearly elliptical shapes of electronic distribution between them. This can also be confirmed by using equation (2) [58,77].…”

“…The covalent bonding character between Sn-X atoms (right part of figure 6) is believed to make considerable contribution to the narrow band gap energies of the compounds. This is in contrast to ionic crystals such as BaLiX 3 (X = F, Cl, Br, I) which have relatively wider electronic band gaps [58]. Figures 6(a)-(c) (right) also illustrate that the covalent character of the Sn-X bonds is quite strong as seen by some accumulation of electrons between Sn and X atoms and by nearly elliptical shapes of electronic distribution between them.…”

“…Table 1 also indicates that the replacement of Cl by Br and I anions leads to an increase in the optimized lattice parameters. This can be attributed to the larger ionic radii of the anions, which is generally true for many halide perovskite compounds [54][55][56][57][58][59][60][61][62][63][64][65][66].…”

“…As a result, less energy will be required to facilitate the free movement of these electrons as conduction electrons within the compounds. This leads to a decrease in the band gap energy of the compounds [58].…”