HP -- A code for the calculation of Hubbard parameters using density-functional perturbation theory

TL;DR

HP is an efficient, open-source implementation of density-functional perturbation theory for calculating Hubbard parameters, reducing computational costs and enabling accurate predictions in complex materials.

Contribution

The paper introduces HP, a novel implementation that computes Hubbard parameters using monochromatic perturbations, avoiding supercell calculations and enhancing efficiency.

Findings

Successfully computed Hubbard parameters for Li$_x$Mn$_{1/2}$Fe$_{1/2}$PO$_4$

Demonstrated accurate predictions of geometry and intercalation voltages

Achieved significant reduction in computational cost

Abstract

We introduce HP, an implementation of density-functional perturbation theory, designed to compute Hubbard parameters (on-site $U$ and inter-site $V$) in the framework of DFT+$U$ and DFT+$U$+$V$. The code does not require the use of computationally expensive supercells of the traditional linear-response approach; instead, unit cells are used with monochromatic perturbations that significantly reduce the computational cost of determining Hubbard parameters. HP is an open-source software distributed under the terms of the GPL as a component of Quantum ESPRESSO. As with other components, HP is optimized to run on a variety of different platforms, from laptops to massively parallel architectures, using native mathematical libraries (LAPACK and FFTW) and a hierarchy of custom parallelization layers built on top of MPI. The effectiveness of the code is showcased by computing Hubbard parameters self-consistently for the phospho-olivine Li$_x$Mn$_{1/2}$Fe$_{1/2}$PO$_4$ ($x=0, 1/2, 1$) and by highlighting the accuracy of predictions of the geometry and Li intercalation voltages.