# ACTIVE_SPACE

Define parameters and method to calculate an electronic active space [Edit on GitHub]

Subsections

- ERI
- ERI_GPW
- FCIDUMP
- LOCALIZE
- PRINT_ORBITAL_CUBES
- SOCKET

## Keywords

- SECTION_PARAMETERS

- ACTIVE_ELECTRONS

- ACTIVE_ORBITALS

- ACTIVE_ORBITAL_INDICES

- AS_SOLVER

- EPS_ITER

- ISOLATED_SYSTEM

- MAX_ITER

- MODEL

- ORBITAL_SELECTION

- QCSCHEMA

- SCF_EMBEDDING

- SUBSPACE_ATOM

- SUBSPACE_SHELL

## Keyword descriptions

SECTION_PARAMETERS: logical = F

  Lone keyword: `T`

  Usage: &ACTIVE_SPACE ON

  Controls the activation of the ACTIVE_SPACE section [Edit on GitHub]

ACTIVE_ELECTRONS: integer = -1

  Usage: ACTIVE_ELECTRONS 4

  The number of active electrons in the CAS space [Edit on GitHub]

ACTIVE_ORBITALS: integer = -1

  Usage: ACTIVE_ORBITALS 2

  The number of active orbitals defining the CAS space. [Edit on GitHub]

ACTIVE_ORBITAL_INDICES: integer[ ] = -1

  Usage: ACTIVE_ORBITAL_INDICES 2 3 {…}

  The indices of the active orbitals. Requires ORBITAL_SELECTION MANUAL! [Edit on GitHub]

AS_SOLVER: enum = NONE

  Usage: AS_SOLVER QISKIT

  Valid values:

  - `NONE` NO solver, used to produce FCIDUMP/QCSchema files

  - `QISKIT` QISKIT active space solver

  The external active space solver for the embedding approach [Edit on GitHub]

EPS_ITER: real = 1.00000000E-006

  Usage: EPS_ITER 1.0E-6

  Energy convergence threshold of the DFT embedding scheme. [Edit on GitHub]

ISOLATED_SYSTEM: logical = F

  Lone keyword: `T`

  System is treated without any periodic boundary conditions. [Edit on GitHub]

MAX_ITER: integer = 50

  Usage: MAX_ITER 50

  Max number of iterations for the DFT embedding scheme. [Edit on GitHub]

MODEL: enum = HARTREE-FOCK

  Usage: MODEL HARTREE-FOCK

  Valid values:

  - `HARTREE-FOCK` Hartree-Fock model for interaction Hamiltonian

  - `RSDFT` Range-separated DFT model for interaction Hamiltonian

  - `DMFT` DMFT model Hamiltonian

  Model used to calculate active space interaction Hamiltonian. [Edit on GitHub]

ORBITAL_SELECTION: enum = CANONICAL

  Usage: ORBITAL_SELECTION CANONICAL

  Valid values:

  - `CANONICAL` Select orbitals using energy ordering of canoncial orbitals

  - `WANNIER_PROJECTION` Select orbitals from projected Wannier functions

  - `MAO` Select orbitals from modified atomic orbitals

  - `MANUAL` Select orbitals manually via ACTIVE_ORBITAL_INDICES

  Method used to select active space orbitals. [Edit on GitHub]

QCSCHEMA: string

  Usage: QCSCHEMA <FILENAME>

  Name of the QCSchema file, may include a path [Edit on GitHub]

SCF_EMBEDDING: logical = F

  Lone keyword: `F`

  Whether to turn on the self-consistent embedding scheme [Edit on GitHub]

SUBSPACE_ATOM: integer = -1

  Usage: SUBSPACE_ATOM x

  Number of atom that defines the subspace to be projected on. [Edit on GitHub]

SUBSPACE_SHELL: string = X

  Usage: SUBSPACE_SHELL 3d4s

  Shell definition for subsapce. [Edit on GitHub]