pyscf

PySCF - Quantum Chemistry Framework

Python library for ab initio electronic structure calculations and quantum chemistry.

When to Use

• Running Hartree-Fock (HF) and Density Functional Theory (DFT) calculations
• Calculating molecular energies and gradients
• Optimizing molecular geometries
• Computing post-HF methods (MP2, CCSD, CI, coupled-cluster)
• Analyzing molecular orbitals and electron density
• Calculating excited states (TD-DFT, CI, EOM-CCSD)
• Computing molecular properties (dipole, charges, NMR, IR)
• Performing periodic calculations (solids, surfaces)
• Benchmarking quantum chemistry methods
• Integrating quantum calculations with ML/AI workflows

Reference Documentation

Official docs: https://pyscf.org/
Search patterns: gto.M, scf.RHF, dft.RKS, mp.MP2, optimize, tddft.TDDFT

Core Principles

Use PySCF For

Task	Module	Example
Build molecule	gto	gto.M(atom='H 0 0 0; H 0 0 1')
Hartree-Fock	scf	scf.RHF(mol).run()
DFT calculation	dft	dft.RKS(mol, xc='B3LYP')
MP2 correlation	mp	mp.MP2(mf).run()
Coupled-cluster	cc	cc.CCSD(mf).run()
Geometry optimization	geomopt	optimize(mf)
Excited states	tddft	tddft.TDDFT(mf).run()
Periodic systems	pbc	pbc.gto.Cell()

Do NOT Use For

• Molecular dynamics simulations (use GROMACS, OpenMM, ASE)
• Very large systems (>1000 atoms) - use semi-empirical or force fields
• Interactive visualization (use PyMOL, VMD)
• High-throughput virtual screening (too slow)
• Real-time quantum simulations

Quick Reference

Installation

# pip (recommended)
pip install pyscf

# With extensions
pip install pyscf[geomopt,dftd3,dmrgscf]

# From conda
conda install -c pyscf pyscf

# Development version
pip install git+https://github.com/pyscf/pyscf

Standard Imports

# Core modules
from pyscf import gto, scf, dft
from pyscf import mp, cc, ci
from pyscf import grad, geomopt
from pyscf import tddft, tdscf
from pyscf import lo, ao2mo

# Tools
from pyscf.tools import molden, cubegen
import numpy as np