Exploring Symmetry-Independent Configurations in KTa_0.5Nb_0.5O₃ Solid Solutions: A First-Principles, QTAIM, and AIMD Approach

Potassium tantaloniobate (KTN) is a lead-free perovskite solid solution with promising electro-optic, ferroelectric, and dielectric applications. Here, we present a systematic first-principles study of KTa_0.5Nb_0.5O₃, exploring all 21 symmetry-independent configurations (SICs) in 2 × 2 × 2 cubic and tetragonal supercells. Configurational energy analysis identifies the most stable atomic arrangements, which are further characterized through band structure, density of states, and quantum theory of atoms in molecules (QTAIM) descriptors. Ab initio molecular dynamics (AIMD) simulations at finite temperature confirm the dynamical robustness of low-energy models and highlight subtle symmetry-dependent fluctuations. The results demonstrate how B-site ordering modulates electronic structure and bonding, offering guidance for the design of compositionally engineered perovskites for electro-optic and dielectric technologies.