Forecasting optical response in lieu of electronic properties of TlCaF₃ via halogen substitution for UV filtration: a DFT perspective

ABSTRACT

It is demonstrated that the substitution of Cl, B, and I at different concentrations in TlCaF₃ significantly alters the phase, electronic band structure and optical, elastic, mechanical and anisotropic properties of the material. At 2.81% and 5.63% concentrations of all substituted elements, the cubic phase of TlCaF₃ transforms into a pseudo-cubic tetragonal phase. With the addition of substitutional atoms, a systematic considerable narrowing of the bandgap is seen, and it can be either direct or indirect depending on the symmetrical positions. The bandgap shrinking can be addressed, in part, via the total/partial/elemental density of states (DOS) in line with structural variations. From the optical response, the refractive index rises with substitution atoms. According to the mechanical stability requirements for each substitution, the determined elastic constants for cubic and tetragonal structures match. Additionally, using elastic parameters, it is possible to estimate the unique mechanical features to evaluate the ductility and brittleness of pure and substituted compounds. Furthernore, Cl, Br and I-atoms’ substitution would make them a suitable choice for improved optimisation in ultraviolet filters (UVF) due to the existence of their absorption spectra in the ultra-violet region and the modification in structural, electrical, optical, elastic and mechanical properties.

KEYWORDS:

• Phase change
• fluctuations in lattice constants
• reduction in bandgap
• ultraviolet filter
• mechanical stability

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All the authors agree with the contents of this manuscript. Not all the paper or any part of this manuscript is under consideration in any journal.

Data availability statement

Data will be made available on reasonable request.