Structural, electronic and elastic properties of KCaF3 and RbCaF3 for vacuum-ultraviolet-transparent lens materials

Abstract

The first principles calculation within the full potential linearized augmented plane wave (FP-LAPW) method is applied to study the structural, electronic and elastic properties of cubic perovskite-type compounds KCaF 3 and RbCaF 3 . The exchange correlation effects are included through the LDA, GGA and modified Becke-Johnson (mBJ) exchange potential. The calculated structural properties such as equilibrium lattice constant, the bulk modulus and its pressure derivative are in good agreement with the available data. KCaF 3 and RbCaF 3 have wide and indirect band gaps and they agree with experimental values. The elastic properties such as elastic constants, anisotropy factor, shear modulus, Young's modulus and Poisson's ratio are obtained for the first time. KCaF 3 and RbCaF 3 are elastically anisotropic and the B/G ratio indicate that these are ductile materials.

DFT study of the electronic properties and the cubic to tetragonal phase transition in RbCaF3

“…The same conclusion is reached for the bulk modulus B, since PBEsol (52.5 GPa) and WC (50.8 GPa) also lead to excellent agreement with experiment (50 GPa), while LDA and PBE lead to overestimation and underestimation, respectively. Compared to the other theoretical works, our results for LDA, PBE, and WC are [27], 6.65 [28] 10.88 [28] 10.9 [46] in agreement with the values in Refs. [25,27].…”

“…As to theoretical approaches, there are a number of ab initio calculations for the cubic phase of RbCaF 3 [25][26][27]27,28] but, to the best of our knowledge, neither the tetragonal phase nor results of density functional theory (DFT) based phonon calculations have been published up to date. It is the purpose of the present work to provide a thorough ab initio investigation of structural, elastic, vibrational, and electronic properties of RbCaF 3 in both, the cubic and the tetragonal phase.…”

Study of Structural and Electronic Properties of Fluoride Perovskite KCaF3 using FP-LAPW Method

“…Our calculated values of a, B, and B' are compared with previous experimental and theoretical results which are mentioned in table 1. We note that the result of the lattice constant obtained within our GGA calculations is slightly higher than the corresponding experimental values [12,18] and calculated value [15,16] but it is slightly less than calculated value [17]. Density of states (DoS) We find from this plot that in the valence region, the total DOS of KCaF 3 showed the occurrence of a maximum peak at 0.31 eV below the Fermi level.…”

“…We also observe from Fig.6 that the maximum band energy occurs at the Fermi level at the symmetry point R. In the conduction band, minimum in energy occurs at 6.4 eV above the Fermi level at the point symmetry Γ and from this plot in Fig.6, we find that it is an indirect type of transition which takes place along R -Γ symmetry directions. The calculated value of indirect band gap is 6.4 eV, which is higher than the calculated value [15] through 0.3 eV and slightly smaller than other calculated value [16].…”

Effect of mixed halide contents on structural, electronic, optical and elastic properties of CsSnI3−xBrx for solar cell applications: first-principles study

“…Later, Cs was replaced by Methyl-ammonium (MA) and Farmamidinium (FA) in CsPbX 3 which resulted in blue shift in band gap with 1.48 eV band gap. But these materials have stability issues [5]. The large size of FA cation leads to FA based perovskites with high tolerance factors t>1 resulting a yellowhexagonal non-perovskite δ-phase at room temperature and found not suitable for solar cell applications [6].…”