ExSCF

ExSCF is a program for methods based on Projected Hartree-Fock, which aims to achieve multireference accuracy with SCF cost.

Pre-requisites

• sympy
• PySCF
• pyscf-forge (optional, for SU-PDFT)
• MOKIT (optional, for read/write fch and CASDFT)
• pyAutoMR (optional)

Of course we need numpy, scipy, etc., but these are also required by PySCF, so they are not listed here.

Installation

• git clone
• add /path/to/ExSCF to your PYTHONPATH

Features

Theoretical features:

• SUHF (Spin-projected Unrestricted Hartree-Fock)
  • energy
  • 1pdm, natural orbitals, 2pdm
• SU-PDFT

not fully tested, or not correct yet:

• SUHF+DFT, SUHF+fDFT, SUHF+fcDFT
• CAS+fDFT, CAS-DFT2
• DeltaSCF with MOM
• PAV-SUMP2, SUMP2(0)

Technical features:

• guess
  • mix (guess.mix)
  • fragment (guess.from_frag)
  • stablize UHF (guess.check_stab)
• converging strategy
  • DIIS (diis_on = True)
  • level_shift = (in a.u.)
• interface (require MOKIT)
  • read guess MO from fch (guess.from_fch_simp)
  • dump MO, NO to fch (tofch = True)

more guess strategies are included in pyAutoMR.

Quick Start

from pyphf import suscf, guess

xyz = 'H 0.0 0.0 0.0; H 0.0 0.0 2.0'''
bas = '3-21g'
mf = guess.mix(xyz, bas, conv='tight')

mf2 = suscf.SUHF(mf)
mf2.kernel()

Contact

For bug report or comments, please contact the author via [email protected] or open an issue.