Theoretical description of structural, electronic, elastic, mechanical, and optical response of Ba1_ xCdxTiO3 for optoelectronic applications

Barium titanate is well-known oxide-based perovskite with numerous potential applications in optoelectronic and energy storage devices. This manuscript aims to present an ab initio study to correlate effect of changes observed in electronic properties with structural, elastic, mechanical, optical and thermodynamic properties as well as acoustic behavior of Cd decorated barium titanate for optoelectronic applications. Cadmium (Cd) inclusion with varying concentrations (x = 0, 0.11, 0.33, 0.55, 0.77, 1) at Barium site was taken into consideration for a systematic study for the tunable character of material. For DFT study, Cambridge Serial Total Energy Package (CASTEP) under generalized gradient approximation was used. Cd substitution at Ba site has turned out to be effective for fine band gap tuning of barium titanate. The band gap gradually decreases except x = 0.11 and make new end material a conductor. Thus provide a way to design a device for optoelectronic application using a tunable band gap mechanism. To investigate the effect of band gap reduction as well as changes observed in other physical quantities, total and partial densities of states along with elemental density of states were computed. It is evident from the results that Cd surely introduces new states in pristine BaTiO3 (BTO), the main cause of electronic change. The question of stability of material was also addressed using extracted mechanical properties from calculated elastic constants and instituted concentrations separately to satisfyBorn's stability criteria.Parameters based on Debye temperature and wave velocity calculations were also extracted to investigate thermodynamic and acoustic behavior of system.Optical response was evaluated and presented comparatively. Refractive index and static dielectric function increase to 3.24 and 10.50 respectively with gradual inclusion of Cd concentration. It is evident that the presented materials are not only lead-free for environmentfriendly energy storage applications but also a promising candidate for solar cell applications because of ideal band gap range. Moreover, improved optical behavior of these materials is claimed to stand out for optoelectronic applications as well as thermoelectric properties.