UCCSD + QSC-EOM (PennyLane/PySCF)

Reference implementation of:

• RHF orbital analysis with PySCF
• UCCSD VQE ground-state optimization with PennyLane
• QSC-EOM excited-state analysis with R1/R2 coefficient export

Repository Layout

• run_exact.py: canonical CLI entrypoint
• SCF.py: RHF + orbital/two-electron integral report generation
• vqe.py: UCCSD VQE optimizer
• qsceom.py: QSC-EOM matrix build + R1/R2 export
• exc.py: determinant/excitation configuration generator
• example/*/run_*.py: per-system runnable examples (H4, H8, N2, CH-)

Requirements

• Python 3.10+
• Dependencies from requirements.txt

python -m venv .venv
source .venv/bin/activate
python -m pip install --upgrade pip
python -m pip install -r requirements.txt

Optional editable install:

python -m pip install -e .
run-exact --help

Quick Start

Run the full H4 pipeline:

python run_exact.py

Run individual stages:

python run_exact.py scf
python run_exact.py vqe
python run_exact.py qsceom

Choose preset systems:

python run_exact.py all --system h4
python run_exact.py all --system h8
python run_exact.py all --system n2
python run_exact.py all --system ch-

Other common options:

python run_exact.py all --max-iter 700
python run_exact.py qsceom --state-idx 1
python run_exact.py all --skip-files
python run_exact.py all --method pyscf

Outputs

By default, the workflow writes:

• fock.txt: SCF orbital summary
• two_elec.txt: antisymmetrized two-electron spin-orbital integrals
• t1_t2.txt: optimized UCCSD amplitudes
• out_r1_r2.txt: QSC-EOM R1/R2 excitation coefficients

Development

python -m py_compile run_exact.py SCF.py vqe.py qsceom.py exc.py fun.py
python run_exact.py --help

Community and GitHub Standards

• Contributions: CONTRIBUTING.md
• Code of conduct: CODE_OF_CONDUCT.md
• Security policy: SECURITY.md
• Pull request template: .github/pull_request_template.md
• Issue templates: .github/ISSUE_TEMPLATE/

License

MIT. See LICENSE.