A configuration interaction (CI) method, operating on all of the orbitals
list of lists; each list has 4 elements, the string of an atom's symbol and atom's x, y, and z coordinates
(optional) equation(s) of the form option = value where option is one of symmetry, unit, davidson_only, lindep, max_memory, max_cycle, max_space, conv_tol, nuclear_gradient, return_rdm, populations, level_shift, pspace_size, conv_tol_hf, diis_hf, diis_space_hf, diis_start_cycle_hf, direct_scf_hf, direct_scf_tol_hf, level_shift_hf, max_cycle_hf, nuclear_gradient_hf, populations_hf
FullCI, also known as full configuration interaction (FCI), performs a configuration interaction calculation over all of the molecular orbitals (MOs). The method solves the Schrödinger equation exactly in the selected basis set.
FullCI scales exponentially in floating-point operations and memory with the number of electrons.
The table of following contents:
float -- total electronic energy of the system
float -- the difference between the FCI energy and the Hartree-Fock energy
Matrix -- coefficients expressing natural molecular orbitals (columns) in terms of atomic orbitals (rows)
Vector -- molecular (natural) orbital occupations
Vector -- string label for each atomic orbital consisting of the atomic symbol and the orbital name
Matrix -- a matrix of CI coefficients whose rows represent α-spin coefficient indices and columns represent β-spin coefficient indices
Matrix -- one-particle reduced density matrix (1-RDM) in the molecular-orbital (MO) representation
Array -- two-particle reduced density matrix (2-RDM) in the molecular-orbital (MO) representation
Vector -- dipole moment according to its x, y and z components
Matrix -- atomic-orbital populations
Vector -- atomic charges from the populations
Matrix -- analytical nuclear gradient
basis = string -- name of the basis set. See Basis for a list of available basis sets. Default is "sto-3g".
spin = nonnegint -- twice the total spin S (= 2S). Default is 0.
charge = nonnegint -- net charge of the molecule. Default is 0.
symmetry = posint/boolean -- is the Schoenflies symbol of the abelian point-group symmetry which can be one of the following: D2h, C2h, C2v, D2, Cs, Ci, C2, C1. true finds the appropriate symmetry while false (default) does not use symmetry.
state = nonnegint -- sets the electronic state to be computed. Default is 0, which is the ground state.
unit = string -- "Angstrom" or "Bohr". Default is "Angstrom".
max_memory = posint -- allowed memory in MB. Default is 4000.
ghost = list of lists -- each list has the string of an atom's symbol and the atom's x, y, and z coordinates. See Ghost Atoms.
initial_mo = Matrix -- Matrix of MOs (columns) in terms of atomic orbitals (rows) that defines the MO basis set.
nuclear_gradient = boolean -- option to return the analytical nuclear gradient if available. Default is false.
return_rdm = string -- options to return the 1-RDM and/or 2-RDM: "none", "rdm1", "rdm1_and_rdm2". Default is "rdm1".
populations = string -- atomic-orbital population analysis: "Mulliken" and "Mulliken/meta-Lowdin". Default is "Mulliken".
conv_tol = float -- converge threshold. Default is 10−18.
davidson_only = boolean -- use the Davidson diagonalization method to find the ground-state eigenvalues.
level_shift = float -- level shift for the Davidson diagonalization. Default is 10−3.
lindep = float -- linear dependence threshold for AH solver. Default is 10−10.
max_cycle = posint -- max number of iterations. Default is 50.
max_space = posint -- space size to hold trial vectors. Default is 12.
nroots = posint -- number of eigenvalues to be computed. When nroots >1, it affects shape of the return value.
pspace_size = posint -- size of Hamiltonian to improve Davidson preconditioner. Default is 50.
ci_response_space = int -- subspace size to solve the CI vector response. Default is 3.
Attributes for Hartree Fock:
conv_tol_hf = float -- converge threshold. Default is 10−10.
diis_hf = boolean -- whether to employ diis. Default is true.
diis_space_hf = posint -- diis's space size. By default, 8 Fock matrices and error vectors are stored.
diis_start_cycle_hf = posint -- the step to start diis. Default is 1.
direct_scf_hf = boolean -- direct SCF in which integrals are recomputed is used by default.
direct_scf_tol_hf = float -- direct SCF cutoff threshold. Default is 10−13.
level_shift_hf = float/int -- level shift (in au) for virtual space. Default is 0.
max_cycle_hf = posint -- max number of iterations. Default is 50.
max_memory_scf_hf = posint -- allowed memory in MB. Default is 4000.
nuclear_gradient_hf = boolean -- option to return the analytical nuclear gradient. Default is false.
populations_hf = string -- atomic-orbital population analysis: "Mulliken" and "Mulliken/meta-Lowdin". Default is "Mulliken".
P. J. Knowles and N. C. Handy, Chem. Phys. Lett. 111, 315-321 1984. "A new determinant-based full configuration interaction method"
J. Olsen, P. Jørgensen, and J. Simons, Chem. Phys. Lett. 169, 463-472 (1990). "Passing the one-billion limit in full configuration-interaction (FCI) calculations"
T. Helgaker, P. Jørgensen, and J. Olsen, Molecular Electronic-Structure Theory (John Wiley & Sons, New York, 2000).
A. Szabo and N. S. Ostlund, Modern Quantum Chemistry: Introduction to Advanced Electronic Structure Theory (Dover Books, New York, 1996).
An full CI calculation of the hydrogen fluoride HF molecule
molecule ≔ H,0,0,0,F,0,0,0.95;
output_hf ≔ FullCImolecule, basis=dz;
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