Desenvolvimento de uma metodologia fisicamente inspirada no princípio da mínima polarizabilidade para o cálculo de propriedades optoeletrônicas de polímeros orgânicos

Abstract

Polymers are macromolecules of significant industrial interest due to their versatility, including their potential application in the design of optical devices. Properties such as the refractive index and Abbe number are closely related to the optical performance of these materials and their technological applications. Therefore, predicting optical properties is essential, as they are directly dependent on the linear polarizability (α), which quantifies the susceptibility of a molecule’s or material’s electronic cloud to distortion under an external electric field. Density Functional Theory based methods employ the electronic density as a fundamental quantity for electronic structure calculations, providing computationally efficient and highly accurate predictions of optical properties in organic materials, such as α. This approach offers a variety of functionals with different levels of correction and approximation for the exchange-correlation potential. Among these, we employ range-separated hybrid (RSH) functionals, which explicitly account for electron-electron interactions by introducing a range-separation parameter (ω), allowing for a transition between short- and long-range interactions. In this study, we investigate the optimization of the ω parameter in RSH functionals based on a physically motivated principle known as the minimal polarizability principle (MPP). The core concept of this approach derives from the maximum hardness principle, which states that a system tends to evolve toward a minimum polarizability value to achieve greater stability. By applying this principle, we developed and assessed a new optimization scheme for the ω parameter in RSH functionals based on MPP and evaluated the impact of this optimization on the optoelectronic properties of organic polymers. The calculated α and refractive index values showed good agreement with experimental data, with higher ω values highlighting the increased contribution of long-range interactions in determining these properties. The polymers investigated to validate the proposed methodology were polythiophene (PT), poly(1,4-phenylene) (PB), trans-polyacetylene (trans-PA), cis-polyacetylene (cis-PA), and polybutadiene (PBT), while the optimized functionals were LC-BLYP, LC-HPBE, and B97XD.