First-principles and semi-empirical calculations for bound hole polarons in KNbO3

TL;DR

This study combines first-principles and semi-empirical methods to investigate hole polarons in KNbO3, predicting both one-site and two-site polarons with similar optical absorption energies, and discusses experimental relevance.

Contribution

It introduces a combined computational approach using LMTO and INDO methods to analyze hole polarons in KNbO3, providing new insights into their nature and energies.

Findings

Predicted existence of one-site and two-site polarons with ~0.9 eV absorption energies.

Used supercells of 40 and 320 atoms for calculations.

Discussed relevance of predictions to experimental data.

Abstract

The ab initio linear muffin-tin-orbital (LMTO) formalism and the semi-empirical method of the Intermediate Neglect of the Differential Overlap (INDO) based on the Hartree-Fock formalism are combined for the study of the hole polarons (a hole trapped nearby the cation vacancy) in a cubic phase of KNbO3 perovskite crystals. The 40-atom and 320-atom supercells were used, respectively. We predict existence of both, one-site and two-site (molecular) polarons with close optical absorption energies (0.9 eV and 0.95 eV). The relevant experimental data are discussed.