LASSCF and CAS-DMET in PySCF
We develop the LASSCF, CAS-DMET, pDMET methods in PySCF as described below
MC-PDFT and LASSCF are both implemented as PySCF-like method classes, pending integration into the main PySCF project:
from mrh.my_pyscf import mcpdft mc = mcpdft.CASSCF (mf, 'tPBE', ncas, nelecas, grids_level=6) mc.kernel ()
where mf is a standard PySCF mean-field method instance. Practical LASSCF calculations often require a reasonably-localized initial guess for the active orbitals, which is provided by the localize_init_guess function:
from mrh.my_pyscf.lasscf_o0 import LASSCF las = LASSCF (mf, (ncas1, ncas2), (nelecas1, nelecas2), spin_sub=(s1, s2)) mo_init = las.localize_init_guess (([0,1,2],[9,10,11])) las.kernel (mo_init)
Here, localize_init_guess localizes the first active subspace, nelecas1 electrons in ncas1 orbitals, to the first three atoms of the molecule; and the second active subspace, nelecas2 electrons in ncas2 orbitals, to atoms 9 through 11. For more information about running MC-PDFT and LASSCF calculations, check out the examples/mcpdft and examples/lasscf folders, respectively, in the source code.The DMET API is somewhat more involved:
from mrh.my_dmet import localintegrals, dmet, fragments myints = localintegrals.localintegrals (mf, range (mf.mol.nao_nr ()), 'meta_lowdin') frag1 = fragments.make_fragment_atom_list (myints, [0,1,2], 'CASSCF(4,4)') frag2 = fragments.make_fragment_atom_list (myints, [3,4,5,6,7,8], 'RHF') frag3 = fragments.make_fragment_atom_list (myints, [9,10,11], 'CASSCF(4,4)') dmet_obj = dmet (myints, [frag1, frag2, frag3]) energy = dmet_obj.doselfconsistent ()
- “Multiconfigurational Self-Consistent Field Theory with Density Matrix Embedding: The Localized Active Space Self-Consistent Field Method,” M. R. Hermes and L. Gagliardi, J. Chem. Theory Comput. 2019, 15, 972.
- “Variational Localized Active Space Self-Consistent Field Method,” M. R. Hermes, R. Pandharkar, and L. Gagliardi, J. Chem. Theory Comput. 2020, 16, 4923.
- “Analytic gradients for state-averaged multiconfiguration pair-density functional theory,” T. R. Scott, M. R. Hermes, A. M. Sand, M. S. Oakley, D. G. Truhlar, and L. Gagliardi, J. Chem. Phys. 2020, 153, 014106.