11. Interfaces to psi4 and pyscf¶
CheMPS2 is currently interfaced with two ab initio quantum chemistry packages:
- The
dmrgplugin to psi4 allows to perform DMRG-CI, DMRG-SCF, and DMRG-CASPT2 calculations with CheMPS2. Since April 2015, CheMPS2 is also an integral part of psi4. - There are also DMRG-CI and DMRG-SCF interfaces between pyscf and CheMPS2.
11.1. psi4 dmrg plugin¶
DMRG-CI, DMRG-SCF, and DMRG-CASPT2 calculations can be performed directly with psi4. The plugin has been tested on psi4-0.5 (released February 17, 2016).
Note that as of late June 2016, DMRG keywords in psi4 have been realigned to those of the chemps2 executable. A translation table is available.
To perform DMRG-CI, DMRG-SCF, and DMRG-CASPT2 calculations, build psi4 or use the conda binary, and then run:
$ cd /mypsi4plugins
$ psi4 --new-plugin dmrg
$ cd dmrg
Now, replace the file dmrg.cc with /sourcefolder/chemps2/integrals/psi4plugins/dmrg.cc. To compile the plugin, the Makefile should be adjusted. Change the line
$(CXX) $(LDFLAGS) -o $@ $^ $(CXXDEFS)
to
$(CXX) $(LDFLAGS) -o $@ $^ $(CXXDEFS) -lchemps2
Remember to add the library and include paths to the Makefile as well, if libchemps2 is not installed in a standard location. For debian/sid, the HDF5 headers are located in the folder /usr/include/hdf5/serial. It might be necessary to add it to the INCLUDES variable in the Makefile.
To compile the plugin, run:
$ make
An example input file to perform a DMRG-CI calculation with the dmrg plugin:
molecule H2O {
0 1
O 0.000000000 0.00 0.000000000
H 0.790689766 0.00 0.612217330
H -0.790689766 0.00 0.612217330
units angstrom
}
sys.path.insert(0, './..')
import dmrg
set basis cc-pVDZ
set reference rhf
set scf_type PK
set e_convergence 1e-13
set d_convergence 1e-13
set ints_tolerance 0.0
set dmrg_irrep 0
set dmrg_multiplicity 1
set restricted_docc [ 1 , 0 , 0 , 0 ]
set active [ 5 , 0 , 4 , 2 ]
set dmrg_sweep_states [ 200, 500, 1000, 1000 ]
set dmrg_sweep_energy_conv [ 1e-8, 1e-8, 1e-8, 1e-8 ]
set dmrg_sweep_max_sweeps [ 5, 5, 5, 100 ]
set dmrg_sweep_noise_prefac [ 0.03, 0.03, 0.03, 0.0 ]
set dmrg_sweep_dvdson_rtol [ 1e-5, 1e-5, 1e-5, 1e-9 ]
set dmrg_print_corr false
set dmrg_mp2_write false
set dmrg_scf_max_iter 1
set dmrg_molden_write true # DMRG-CI pseudocanonical orbitals
set dmrg_opdm_ao_print true # DMRG-CI density in the AO basis
energy('dmrg')
Note that the option dmrg_max_iter has been set to 1, so that only one active space calculation is performed. This file (H2O.dmrgci.in) should be placed in the folder /mypsi4plugins/dmrg. The DMRG-CI calculation can then be started with:
$ cd /mypsi4plugins/dmrg
$ psi4 H2O.dmrgci.in H2O.dmrgci.out
An example input file to perform a DMRG-SCF calculation with the dmrg plugin:
molecule O2 {
O 0.0 0.0 0.0
O 0.0 0.0 3.0
units au
}
sys.path.insert(0, './..')
import dmrg
set basis cc-pVDZ
set reference rhf
set scf_type PK
set dmrg_irrep 0
set dmrg_multiplicity 1
set restricted_docc [ 1 , 0 , 0 , 0 , 0 , 1 , 0 , 0 ]
set active [ 2 , 0 , 2 , 2 , 0 , 2 , 2 , 2 ]
set dmrg_sweep_states [ 500, 1000, 1000 ]
set dmrg_sweep_energy_conv [ 1e-10, 1e-10, 1e-10 ]
set dmrg_sweep_max_sweeps [ 5, 5, 10 ]
set dmrg_sweep_noise_prefac [ 0.05, 0.05, 0.0 ]
set dmrg_sweep_dvdson_rtol [ 1e-5, 1e-5, 1e-9 ]
set dmrg_print_corr false
set dmrg_mps_write false
set dmrg_scf_grad_thr 1e-6
set dmrg_unitary_write true
set dmrg_diis true
set dmrg_scf_diis_thr 1e-2
set dmrg_diis_write true
set dmrg_scf_max_iter 100
set dmrg_excitation 1 # First excited state
set dmrg_scf_state_avg true
set dmrg_scf_active_space NO # INPUT; NO; LOC
set dmrg_local_init false
set dmrg_molden_write true # Converged DMRG-SCF pseudocanonical orbitals
set dmrg_opdm_ao_print true # Converged DMRG-SCF density in the AO basis
energy('dmrg')
This file (O2.dmrgscf.in) should be placed in the folder /mypsi4plugins/dmrg. The DMRG-SCF calculation can then be started with:
$ cd /mypsi4plugins/dmrg
$ psi4 O2.dmrgscf.in O2.dmrgscf.out
An example input file to perform a DMRG-CASPT2 calculation with the dmrg plugin:
molecule N2 {
N 0.0000 0.0000 0.0000
N 0.0000 0.0000 2.1180
units au
}
sys.path.insert(0, './..')
import dmrg
set basis cc-pVDZ
set reference rhf
set scf_type PK
set e_convergence 1e-12
set d_convergence 1e-12
set dmrg_irrep 0
set dmrg_multiplicity 1
set restricted_docc [ 1 , 0 , 0 , 0 , 0 , 1 , 0 , 0 ]
set active [ 2 , 0 , 1 , 1 , 0 , 2 , 1 , 1 ]
set dmrg_sweep_states [ 500, 1000, 1000 ]
set dmrg_sweep_energy_conv [ 1e-10, 1e-10, 1e-10 ]
set dmrg_sweep_max_sweeps [ 5, 5, 10 ]
set dmrg_sweep_noise_prefac [ 0.05, 0.05, 0.0 ]
set dmrg_sweep_dvdson_rtol [ 1e-5, 1e-5, 1e-9 ]
set dmrg_print_corr false
set dmrg_mps_write false
set dmrg_scf_grad_thr 1e-6
set dmrg_unitary_write true
set dmrg_diis true
set dmrg_scf_diis_thr 1e-2
set dmrg_diis_write true
set dmrg_scf_max_iter 100
set dmrg_excitation 0 # Ground state
set dmrg_scf_state_avg false
set dmrg_scf_active_space INPUT # INPUT; NO; LOC
set dmrg_local_init false
set dmrg_molden_write false # Converged DMRG-SCF pseudocanonical orbitals
set dmrg_opdm_ao_print true # Converged DMRG-SCF density in the AO basis
set dmrg_caspt2_calc true
set dmrg_caspt2_orbs ACTIVE
set dmrg_caspt2_ipea 0.00
set dmrg_caspt2_imag_shift 0.00
energy('dmrg')
This file (N2.caspt2.in) should be placed in the folder /mypsi4plugins/dmrg. The DMRG-CASPT2 calculation can then be started with:
$ cd /mypsi4plugins/dmrg
$ psi4 N2.caspt2.in N2.caspt2.out
Since April 2015, CheMPS2 is also an integral part of psi4. Please consult psi4‘s documentation on how to run DMRG-CI, DMRG-SCF, and DMRG-CASPT2 calculations with psi4.
11.2. pyscf¶
pyscf is a new quantum chemistry package, in which all layers are written or interfaced in python. In the future, the package will be able to perform DMRG-CI and DMRG-SCF calculations using PyCheMPS2: chemps2.py.
Examples of how to extract MO integrals from pyscf to perform DMRG-CI calculations with PyCheMPS2 can be found in:
/sourcefolder/chemps2/integrals/pyscf/example.py/sourcefolder/chemps2/integrals/pyscf/example2.py/sourcefolder/chemps2/integrals/pyscf/example3.py/sourcefolder/chemps2/integrals/pyscf/dmrgci.py/sourcefolder/chemps2/integrals/pyscf/call_chemps2.py
Please remember to append the correct pyscf and PyCheMPS2 directories to sys.path at the top of these files.
