19.3. Example Python scripts

Several complete examples can be found in the directory data/examples/rsf.

19.3.1. RSF-RCCD calculations on the C atom with 4 unpaired electrons

This script provides a basic example of an RSF calculation using an RCCD reference in PyBEST. It is executed for the carbon atom with the cc-pVDZ basis set, targeting a quintet state.

Listing 19.1 data/examples/rsf/rsf_ccd_c_cc-pvdz.py

#!/usr/bin/env python3

from pybest import context
from pybest.cc import RCCD
from pybest.gbasis import (
    compute_cholesky_eri,
    compute_kinetic,
    compute_nuclear,
    compute_nuclear_repulsion,
    compute_overlap,
    get_gobasis,
)
from pybest.linalg import CholeskyLinalgFactory
from pybest.occ_model import AufbauOccModel
from pybest.rsf_eom import RSFCCD
from pybest.wrappers import RHF

#
# Set up molecule, define basis set
#
# get the XYZ file from PyBEST's test data directory
c_xyz = context.get_fn("test/c.xyz")
basis = get_gobasis("cc-pvdz", c_xyz)

#
# Define Occupation model, orbitals and overlap
#
lf = CholeskyLinalgFactory(basis.nbasis)
orb_a = lf.create_orbital(basis.nbasis)
olp = compute_overlap(basis)

occ_model = AufbauOccModel(basis)

#
# Construct Hamiltonian
#
kin = compute_kinetic(basis)
ne = compute_nuclear(basis)
eri = compute_cholesky_eri(basis)
external = compute_nuclear_repulsion(basis)

#
# Do a Hartree-Fock calculation
#
hf = RHF(lf, occ_model)
hf_output = hf(kin, ne, eri, external, olp, orb_a)

#
# Do CCD optimization
#
ccd = RCCD(lf, occ_model)
ccd_output = ccd(kin, ne, eri, hf_output)

#
# Do RSF-CCD calculation with 4 unpaired electrons
#
rsf = RSFCCD(lf, occ_model, alpha=4)
rsf_output = rsf(kin, ne, eri, ccd_output, nroot=3)

19.3.2. RSF-RLCCSD calculations on the C atom with 4 unpaired electrons

This script provides a basic example of an RSF calculation using an RLCCSD reference in PyBEST. It is executed for the carbon atom with the cc-pVDZ basis set, targeting a quintet state.

Listing 19.2 data/examples/rsf/rsf_lccsd_c_cc-pvdz.py

from pybest import context
from pybest.cc import RLCCSD
from pybest.gbasis import (
    compute_eri,
    compute_kinetic,
    compute_nuclear,
    compute_nuclear_repulsion,
    compute_overlap,
    get_gobasis,
)
from pybest.linalg import DenseLinalgFactory
from pybest.occ_model import AufbauOccModel
from pybest.rsf_eom import RSFLCCD
from pybest.wrappers import RHF

#
# Set up molecule, define basis set
#
# get the XYZ file from PyBEST's test data directory
c_xyz = context.get_fn("test/c.xyz")
basis = get_gobasis("cc-pvdz", c_xyz)

#
# Define Occupation model, orbitals and overlap
#
lf = DenseLinalgFactory(basis.nbasis)
orb_a = lf.create_orbital(basis.nbasis)
olp = compute_overlap(basis)

occ_model = AufbauOccModel(basis)

#
# Construct Hamiltonian
#
kin = compute_kinetic(basis)
ne = compute_nuclear(basis)
eri = compute_eri(basis)
external = compute_nuclear_repulsion(basis)

#
# Do a Hartree-Fock calculation
#
hf = RHF(lf, occ_model)
hf_output = hf(kin, ne, eri, external, olp, orb_a)

#
# Do LCCSD optimization
#
lccd = RLCCSD(lf, occ_model)
lccd_output = lccd(kin, ne, eri, hf_output)

#
# Do RSF-LCCSD calculation with 4 unpaired electrons
#
rsf_L = RSFLCCD(lf, occ_model, alpha=4)
rsf_L_output = rsf_L(kin, ne, eri, lccd_output, nroot=8)

19.3.3. RSF-RfpCCSD calculations on the C atom with 4 unpaired electrons

This script provides a basic example of an RSF calculation using an RfpCCSD reference in PyBEST. The reference is obtained via an initial RpCCD step. It is executed for the carbon atom with the cc-pVDZ basis set, targeting a quintet state.

Listing 19.3 data/examples/rsf/rsf_fpccsd_c_cc-pvdz.py

from pybest import context
from pybest.cc import RfpCCSD
from pybest.gbasis import (
    compute_eri,
    compute_kinetic,
    compute_nuclear,
    compute_nuclear_repulsion,
    compute_overlap,
    get_gobasis,
)
from pybest.geminals import RpCCD
from pybest.linalg import DenseLinalgFactory
from pybest.occ_model import AufbauOccModel
from pybest.rsf_eom import RSFfpCCSD
from pybest.wrappers import RHF

#
# Set up molecule, define basis set
#
# get the XYZ file from PyBEST's test data directory
c_xyz = context.get_fn("test/c.xyz")
basis = get_gobasis("cc-pvdz", c_xyz)

#
# Define Occupation model, orbitals and overlap
#
lf = DenseLinalgFactory(basis.nbasis)
orb_a = lf.create_orbital(basis.nbasis)
olp = compute_overlap(basis)

occ_model = AufbauOccModel(basis)

#
# Construct Hamiltonian
#
kin = compute_kinetic(basis)
ne = compute_nuclear(basis)
eri = compute_eri(basis)
external = compute_nuclear_repulsion(basis)

#
# Do a Hartree-Fock calculation
#
hf = RHF(lf, occ_model)
hf_output = hf(kin, ne, eri, external, olp, orb_a)

#
# Do pCCD optimization
#
pccd = RpCCD(lf, occ_model)
pccd_output = pccd(kin, ne, eri, hf_output)

#
# Do fpCCSD optimization
#
fpccsd = RfpCCSD(lf, occ_model)
fpccsd_output = fpccsd(kin, ne, eri, pccd_output)

#
# Do RSF-fpCCSD calculation with 4 unpaired electrons
#
rsf_fp = RSFfpCCSD(lf, occ_model, alpha=4)
rsf_fp_output = rsf_fp(kin, ne, eri, fpccsd_output, nroot=8)

19.3.4. RSF-RfpLCCSD calculations on the C atom with 4 unpaired electrons

This script provides a basic example of an RSF calculation using an RfpLCCSD reference in PyBEST. The reference is obtained via an initial RpCCD step. It is executed for the carbon atom with the cc-pVDZ basis set, targeting a quintet state.

Listing 19.4 data/examples/rsf/rsf_fplccsd_c_cc-pvdz.py

from pybest import context
from pybest.cc import RpCCDLCCSD
from pybest.gbasis import (
    compute_eri,
    compute_kinetic,
    compute_nuclear,
    compute_nuclear_repulsion,
    compute_overlap,
    get_gobasis,
)
from pybest.geminals import RpCCD
from pybest.linalg import DenseLinalgFactory
from pybest.occ_model import AufbauOccModel
from pybest.rsf_eom import RSFfpLCCSD
from pybest.wrappers import RHF

#
# Set up molecule, define basis set
#
# get the XYZ file from PyBEST's test data directory
c_xyz = context.get_fn("test/c.xyz")
basis = get_gobasis("cc-pvdz", c_xyz)

#
# Define Occupation model, orbitals and overlap
#
lf = DenseLinalgFactory(basis.nbasis)
orb_a = lf.create_orbital(basis.nbasis)
olp = compute_overlap(basis)

occ_model = AufbauOccModel(basis)

#
# Construct Hamiltonian
#
kin = compute_kinetic(basis)
ne = compute_nuclear(basis)
eri = compute_eri(basis)
external = compute_nuclear_repulsion(basis)

#
# Do a Hartree-Fock calculation
#
hf = RHF(lf, occ_model)
hf_output = hf(kin, ne, eri, external, olp, orb_a)

#
# Do pCCD optimization
#
pccd = RpCCD(lf, occ_model)
pccd_output = pccd(kin, ne, eri, hf_output)

#
# Do fpLCCSD optimization
#
fplccsd = RpCCDLCCSD(lf, occ_model)
fplccsd_output = fplccsd(kin, ne, eri, pccd_output)

#
# Do RSF-fpLCCSD calculation with 4 unpaired electrons
#
rsf_fpl = RSFfpLCCSD(lf, occ_model, alpha=4)
rsf_fpl_output = rsf_fpl(kin, ne, eri, fplccsd_output, nroot=8)