H-wave - A Python package for the Hartree-Fock approximation and the random phase approximation

H -wave is an open -source software package for performing the Hartree-Fock approximation (HFA) and random phase approximation (RPA) for a wide range of Hamiltonians of interacting fermionic systems. In HFA calculations, H -wave examines the stability of several symmetry -broken phases, such as anti -ferromagnetic and charge -ordered phases, in the given Hamiltonians at zero and finite temperatures. Furthermore, H -wave calculates the dynamical susceptibilities using RPA to examine the instability toward the symmetry -broken phases. By preparing a simple input file for specifying the Hamiltonians, users can perform HFA and RPA for standard Hamiltonians in condensed matter physics, such as the Hubbard model and its extensions. Additionally, users can use a WANNIER90-like format to specify fermionic Hamiltonians. A WANNIER90 format is implemented in RESPACK to derive ab initio Hamiltonians for solids. HFA and RPA for the ab initio Hamiltonians can be easily performed using H -wave. In this paper, we first explain the basis of HFA and RPA, and the basic usage of Hwave, including download and installation. Thereafter, the input file formats implemented in H -wave, including the WANNIER90-like format for specifying the interacting fermionic Hamiltonians, are discussed. Finally, we present several examples of H -wave such as zero -temperature HFA calculations for the extended Hubbard model on a square lattice, finite -temperature HFA calculations for the Hubbard model on a cubic lattice, and RPA in the extended Hubbard model on a square lattice. Program summary Program Title: H -wave CPC Library link to program files: https://doi .org /10 .17632 /9gr6pxhfjm .1 Developer's repository link: https://github .com /issp -center -dev /H -wave Code Ocean capsule: https://codeocean .com /capsule /6875177 Licensing provisions: GNU General Public License version 3 Programming language: Python3 External routines/libraries: NumPy, SciPy, Tomli, Requests. Nature of problem: Physical properties of strongly correlated electrons are examined such as ground state phase structure and response functions at zero and finite temperatures. Solution method: Calculations based on the unrestricted Hartree-Fock approximation and the random phase approximation are performed for the quantum lattice models such as the Hubbard model and its extensions.