Weighted Density Functionals for Ferroelectric Materials

TL;DR

This paper explores the application of weighted density functionals to ferroelectric materials, demonstrating improved accuracy over traditional methods in electronic structure calculations and ferroelectric soft mode predictions.

Contribution

It introduces the implementation of the weighted density approximation for ferroelectric materials and shows its advantages over local density and generalized gradient approximations.

Findings

Weighted density approximation outperforms LDA and GGA for ground state calculations.

Electronic structures are minimally affected by the new approximation.

Predicted ferroelectric soft mode in KNbO₃ is about 20% smaller than experimental estimates.

Abstract

The weighted density approximation, its implementation and its application to ferroelectric materials is discussed. Calculations are presented for several perovskite oxides and related materials. In general the weighted density approximation is found to be superior to either the local density or generalized gradient approximation for the ground state. Electronic structures are little changed. The linear response of the weighted density approximation is calculated for the homogeneous electron gas, and found to be improved relative to the local density result, but not in full agreement with existing Monte Carlo data. It is shown that the agreement can be further improved by a simple modification. Calculations of the ferroelectric soft mode in KNbO$_3$ suggest that the low temperature distortion is approximately 20% smaller than indicated by existing experiments.