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

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 usage of computationally expensive supercells of the traditional linear-response approach; instead, unit cells are used with monochromatic perturbations that significantly reduces the computational cost of determining Hubbard parameters. HP is 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 intercalation voltages.

Electronic structure and magnetism of pristine and Fe-doped $α$-MnO$_2$ from density-functional theory with extended Hubbard functionals

“…DFT+U and DFT+U +V calculations were performed using the Löwdin-orthogonalized atomic orbitals as Hubbard projector functions [68,69]. Hubbard U and V parameters were computed using DFPT [52,53] as implemented in the HP code [85] which is part of Quantum ESPRESSO. Hubbard parameters are listed in Tables I and III, and they will be discussed in detail in the following.…”