HORTON (software)

HORTON, the Helpful Open-source Research TOol for N-fermion systems, is an open source modular quantum chemistry program written primarily in Python. It is composed of several quantum mechanical methods for electronic structure calculations and tools for post-processing wave functions and densities.
Capabilities
Electronic Structure Methods
* Hartree-Fock and DFT methods:
** Restricted and unrestricted
** Various LDA, GGA and Hybrid GGA functionals
** Various SCF algorithms: ordinary SCF, optimal damping scf, CDIIS, SCF, EDIIS SCF, combination of CIIS and EDIIS
* Geminals-based methods: AP1roG
* Perturbation theory: MP2 from restricted HF, PTa of AP1roG, PTb of AP1roG
* Custom Hamiltonians:
* Molecular electronic Hamiltonians
* Model Hamiltonians: 1D Hubbard model
* User-provided Hamiltonians
Post-processing
* Atoms-In-Molecule analysis: Becke, Hirshfeld, Iterative Hirshfeld, Iterative Stockholder, Extended Hirshfeld
* Electrostatic potential fitting of atomic charges
* Orbital entanglement analysis
* Orbital localization: Pipek-Mezey
Compatibility with other quantum chemistry software
* Supports geometry input and output: xyz, POSCAR, and cif* file formats
* Supports cube input: Gaussian cube, VASP CHGCAR and LOCPOT formats
* Supports cube output: Gaussian cube format
* Supports wavefunction input: Gaussian fchk, molden, Molekel, and wfn formats
* Supports wavefunction output: molden format
* Supports Hamiltonian input: Molpro FCIDUMP and Gaussian log formats
* Supports Hamiltonian output: Molpro FCIDUMP format