Determine the optimal modeling parameters for perovskite-oxide phonons

Determine the exchange-correlation functional and harmonic-approximation parameter setting that most accurately describes the phonon properties of perovskite oxides, particularly the soft transverse-optical Slater mode governing their Pockels response.

Background

The paper calculates Pockels coefficients using density-functional theory within the harmonic approximation and finds that the soft Slater phonon mode dominates the technologically important response. The calculated mode frequencies, however, differ substantially from experimentally measured values, causing significant errors in the predicted Pockels coefficients.

The authors attribute this difficulty to the sensitivity of perovskite-oxide phonon properties to both the exchange-correlation functional and the harmonic approximation. They state that the best parameter setting has not yet been identified, leaving unresolved which computational treatment can reliably reproduce the relevant soft-mode behavior without replacing calculated frequencies by experimental measurements.