6.20.3 Job Control for iFCI

IFCI_TUPLES
       Level of $n$-body expansion to solve. Note that $n>2$ can be computationally costly.
TYPE:
       INTEGER
DEFAULT:
       Must be set.
OPTIONS:
       1 $n=1$ 2 $n=2$ 3 $n=3$ 4 $n=4$
RECOMMENDATION:
       Use $n=2$ for initial system analysis, $n>2$ for higher accuracy.

IFCI_READ
       Restarts iFCI with existing TUPLES_1E_DATA file, if it exists.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Start from scratch 1 Restart from previous file
RECOMMENDATION:
       Use 0 if no previous run files exist. Use 1 if intending to restart from previous data.

IFCI_TRIPLETS
       Set state to solve.
TYPE:
       INTEGER
DEFAULT:
       0
OPTIONS:
       0 Singlet 1 Triplet 2 Quintet
RECOMMENDATION:
       None

IFCI_ZETA
       Convergence for each iFCI increment. Note that the format is $\zeta =$ IFCI_ZETA$/10$.
TYPE:
       INTEGER
DEFAULT:
       55
OPTIONS:
       45 Loose 55 Moderate 65 Tight 75 Tighter 85 Quite tight 95 Maximum
RECOMMENDATION:
       Use 65 and increase to 75 to check convergence.

HBCI_EPS1
       Determines dimension of HBCI space.
TYPE:
       INTEGER
DEFAULT:
       1000
OPTIONS:
       $N$ HBCI ${\epsilon }_1$ in $\mu$ E${}_{\mathrm{h}}$
RECOMMENDATION:
       Use default or 500 for tighter convergence.

IFCI_TUPLE_THRESH
       Collapse near-degenerate geminals within threshold into one body.
TYPE:
       INTEGER
DEFAULT:
       2500
OPTIONS:
       $n$ in $\mu$E${}_{\mathrm{h}}$
RECOMMENDATION:
       Use default unless there are sets of highly correlating occupied orbitals.

IFCI_TRIPLES_SCREEN
       Cutoff (${𝒞}_3$) for determining if a 3-body term is significant.
TYPE:
       INTEGER
DEFAULT:
       1000
OPTIONS:
       $n$ where ${𝒞}_3={10}^{-\zeta }\times n$ in E${}_{\mathrm{h}}$
RECOMMENDATION:
       Use the default unless looser (higher $n$) or tighter (lower $n$) consideration of triads for a given system is desired. Setting to 0 computes all triads (costly).

IFCI_QUAD_SCREEN
       Cutoff (${𝒞}_4$) for determining if a 4-body term is significant.
TYPE:
       INTEGER
DEFAULT:
       IFCI_TRIPLES_SCREEN
OPTIONS:
       $n$ where ${𝒞}_4={10}^{-\zeta }\times n$ in E${}_{\mathrm{h}}$
RECOMMENDATION:
       Same as IFCI_TRIPLES_SCREEN but note that $4$-body terms are significantly more costly.

IFCI_STATE_ADD
       Adds additional states to HBCI solver when there is degeneracy amongst states.
TYPE:
       INTEGER
DEFAULT:
       10
OPTIONS:
       $n$ Add states within $n$ mE${}_{\mathrm{h}}$
RECOMMENDATION:
       Use default unless it is known that degenerate states are present.

IFCI_PRINT
       Larger number gives more output.
TYPE:
       INTEGER
DEFAULT:
       2
OPTIONS:
       1 Minimal output 2 Readable output 3 Extra output 4 Excessive output 5+ Bug testing output
RECOMMENDATION:
       2 is recommended, 1-3 is appropriate, larger than 4 is unnecessary (consider yourself warned).

IFCI_NO_THRESH
       Equivalent to HBCI ${\epsilon }_1$ for increment-specific NO generation step.
TYPE:
       INTEGER
DEFAULT:
       1000
OPTIONS:
       $n$ in $\mu$E${}_{\mathrm{h}}$
RECOMMENDATION:
       Set to equal HBCI_EPS1.

IFCI_REF_ITER
       Use HF or PP reference density.
TYPE:
       INTEGER
DEFAULT:
       1
OPTIONS:
       0 HF 1 PP
RECOMMENDATION:
       Use 0.

IFCI_OCC
       Specifies the number of active occupied orbitals.
TYPE:
       INTEGER
DEFAULT:
       Full valence.
OPTIONS:
       $n$ Include $n$ orbitals in the active space $-1$ Full valence
RECOMMENDATION:
       Use full valence active space.