Pseudopotentials, an overlooked source and remedy of DFT errors

TL;DR

This paper reveals that pseudopotentials significantly contribute to errors in DFT calculations, and proposes atomic-level adjusted pseudopotentials as a practical correction method that improves accuracy beyond standard approaches.

Contribution

It introduces atomic-level adjusted pseudopotentials that correct DFT errors and demonstrates their effectiveness in accurately predicting semiconductor bandgaps.

Findings

Eliminated erroneous metal predictions for 11 compounds.

Reduced mean relative error from 80% to 20%.

Achieved accuracy surpassing hybrid functionals and GW methods.

Abstract

First-principles calculations rely heavily on pseudopotentials, yet their impact on accuracy is hardly addressed. In this work, we show that most pseudopotentials to date introduce errors, which manifest themselves as errors of atomic energy levels, leading to a $de facto$ deviation from the Hohenberg-Kohn theorem. We consider the atomic-level adjusted pseudopotentials, whose interplay with exchange-correlation functional provides a pragmatic correction that balances accuracy and efficiency. We benchmark our theory with bandgap calculation for 54 semiconductors containing monovalent Cu. The results, compared to those from conventional studies, not only remove all erroneous metal predictions for 11 compounds, but also reduce the mean relative error from 80\% to 20\%. Overall accuracy even exceeds those of standard hybrid functionals and GW methods.