First-principles calculations of electronic and optical properties of lead-free KTa_1-xNb_xO₃ under high pressure

The structural, electronic and optical properties of lead-free KTa _1-xNb_xO₃ (KTN) under high pressures have been investigated using the first-principles calculations. The computed results at ambient pressure are in excellent agreement with available theoretical and experimental data. We found that the application of high pressure leads to the obvious variation of optical properties. Our calculations show that the optical absorption edge of KTN is redshifted with increasing pressure. Above 100 GPa the band gap decreases rapidly, indicating that KTN may be metallic if pressure is high enough. It has been found that plasma frequency can be continuously adjustable by applying pressures.