# Comparative first-principles studies of prototypical ferroelectric materials by LDA, GGA, and SCAN meta-GGA

## TL;DR

This study compares the performance of LDA, GGA, and SCAN meta-GGA functionals in first-principles calculations of diverse ferroelectric materials, demonstrating that SCAN offers significant improvements in accuracy and predictive power.

## Contribution

It introduces the SCAN meta-GGA functional as a superior alternative for studying ferroelectric properties across different bonding types in materials.

## Key findings

- SCAN significantly improves structural and energetic predictions.
- GGA performs better for hydrogen-bonded ferroelectrics.
- LDA is more accurate for conventional perovskite ferroelectrics.

## Abstract

Originating from a broken spatial inversion symmetry, ferroelectricity is a functionality of materials with an electric dipole that can be switched by external electric fields. Spontaneous polarization is a crucial ferroelectric property, and its amplitude is determined by the strength of polar structural distortions. Density functional theory (DFT) is one of the most widely used theoretical methods to study ferroelectric properties, yet it is limited by the levels of approximations in electron exchange-correlation. On the one hand, the local density approximation (LDA) is considered to be more accurate for the conventional perovskite ferroelectrics such as BaTiO3 and PbTiO3 than the generalized gradient approximation (GGA), which suffers from the so-called super-tetragonality error. On the other hand, GGA is more suitable for hydrogen-bonded ferroelectrics than LDA, which largely overestimates the strength of hydrogen bonding in general. We show here that the recently developed general-purpose strongly constrained and appropriately normed (SCAN) meta-GGA functional significantly improves over the traditional LDA/GGA for structural, electric, and energetic properties of diversely-bonded ferroelectric materials with a comparable computational effort, and thus enhances largely the predictive power of DFT in studies of ferroelectric materials. We also address the observed system-dependent performances of LDA and GGA for ferroelectrics from a chemical bonding point of view.

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Source: https://tomesphere.com/paper/1702.04817