ebcc: Coupled cluster calculations on electron-boson systems

The ebcc package implements various coupled cluster (CC) models for both purely electronic and coupled electron-boson models, with a focus on generality and model extensibility.

Installation

From source:

git clone https://github.com/BoothGroup/ebcc
pip install .

Usage

The implemented models are built upon the mean-field objects of pyscf:

from pyscf import gto, scf
from ebcc import EBCC
mol = gto.M(atom="H 0 0 0; H 0 0 1", basis="cc-pvdz")
mf = scf.RHF(mol)
mf.kernel()
ccsd = EBCC(mf)
ccsd.kernel()

Code generation

The models implemented are generated algorithmically from expressions over second quantized operators. Expressions are generated using qwick and pdaggerq with optimisation of common subexpressions and contraction order achieved using drudge and gristmill. User-inputted models should operate seamlessly with the solvers by adding files under ebcc/codegen, so long as they satisfy the interface.