26.5 Options

Various options can be specified using key/value pairs qualifying the LOCAL or MULTP command. For all options appropriate default values are set, and so these options must usually be modified only for special purposes. For convenience and historical reasons, alias names are available for various options, which correspond to the variable name used in the program. Table 9 summarizes the keys, aliases and default values. In the following, the parameters are described in more detail.

Table 9: Summary of local (multp) options and their default values

Parameter	Alias	Default value	Meaning
General Parameters:
LOCAL		4	determines which program to use
SAVE	SAVDOM	0	specifies record for saving domain info
START	RESTDOM	0	specifies record for reading domain info
PIPEK	LOCORB	0	activates or deactivates PM localization
SAVORB	SAVLOC	0	specifies record for saving local orbitals
DOMONLY		0	if set, only domains are made.
			if 2, only orbital domains are made.
Parameters to select weak and distant pairs:
WEAKPAIR	WEAKP	1	criterion for selection of weak pairs
DISTPAIR	DISTP	0 (8)	criterion for selection of distant pairs
VERYDIST	VERYD	0 (15)	criterion for selection of very distant pairs
Parameters to define domains:
DOMSEL	CHGFRAC	0.98	selection criterion for orbital domains
DELCOR	IDLCOR	2	delete projected core AOs up to certain shell
DELBAS	IBASO	0	determines how to remove redundancies
Parameters for redundancy check using DOMSEL=1
TYPECHECK	TYPECHK	1	activates basis function type restrictions
DELSHL	IDLSHL	1	determines if whole shells are to be deleted
DELEIG	IDLEIG	1	determines how to select redundant functions
DELCMIN	CDELMIN	0.1	parameter for use with DELEIG=1
Parameter for multipole treatment of exchange operators:
DSTMLT		0 (3)	expansion level for distant pairs
Parameters for energy partitioning:
IEPART		0	If nonzero: do energy partitioning
EPART		3.0	cutoff parameter for determining individual monomers
Miscellaneous options:
SKIPDIST	SKIPD	3	determines at which stage weak and distant pairs are eliminated
ASYDOM	JITERM	0	parameter for use of asymmetric domains
LOCSING	LOCSNG	0	determines virtual space used for singles
MAXANG	MAXL	99	restriction for Boughton-Pulay domain selection
CHGMIN		0.01	minimum Mulliken charge for BP domain selection
CHGMINH		0.05	minimum Mulliken charge of H-atoms for BP domain selection
CHGMAX		0.40	If charge larger than this value, atom is always included
MAXBP	MAXBP	0	determines how to rank atoms in Boughton-Pulay domain selection
MULLIKEN	LOCMUL	0	determines how to rank atoms for domains
PIPEKAO	LOCAO	0	activates AO localization criterion
NONORM		2	determines whether projected functions are normalized
LMP2ALGO	MP2ALGO	1	if nonzero, use low-order scaling method in LMP22 iterations
OLDDEF		0	allows to revert to older defaults
Thresholds:
THRPIP		1.d-12	Threshold for Pipek-Mezey localization.
THRORB		1.d-6	Threshold for eliminating projected orbitals with small norm.
THRLOC		1.d-6	Threshold for eliminating redundant projected orbitals.
THRCOR		1.d-1	Threshold for eliminating projected core orbitals.
THRMP2		1.d-8	Threshold for neglecting small fock matrix elements in the
			LMP2 iteration.

General Parameters:

LOCAL=local

Determines which method is used:
LOCAL=0: Conventional (non-local) calculation.
LOCAL=1: Local method is simulated using canonical MOs. The local basis is used only at an intermediate stage to update the amplitudes in each iteration (only for testing).
LOCAL=2: Calculation is done in local basis, but without using local blocking (i.e. full matrices are used). This is the most expensive method and only for testing.
LOCAL=3: Fully local calculation. This is the fastest method for local calculations with no weak pairs.
LOCAL=4: Fully local calculation (Default). This is the fastest method for large molecules with many weak pairs and requires minimum memory.

SAVE=record

Allows the domain information to be saved on record=name.ifil for later restart using START. This can be used to freeze the domains as function of geometry. Note that the domain information is automatically stored if a SAVE directive is given (see above), and in this case the record given on the SAVE card will overwrite any record given as SAVE option.

START=record

Retrieves domain information previously saved using SAVE. Note that the domain information is automatically restored if a START directive is given (see above), and in this case the record given on the START card will overwrite any record given as START option.

PIPEK=option

If this option is given and option$\gt 0$, the orbitals are localized using the Pipek-Mezey technique. If this option is not given or option=0 (default), the orbitals are localized unless localized orbitals are found in the orbital record (cf. ORBITAL and LOCALIZE directives). In the latter case, the most recent localized orbitals are used. Setting option=-1 switches the localization off. If option$\gt 1$ the localized orbitals are printed. Note: Boys localization can only be performed using the LOCALIZE command. The program will use the Boys orbitals if they are found in the orbital record and the PIPEK option is absent or option$\le 0$.

SAVORB=record

Allows the localized and projected orbitals to be saved on record=name.ifil for later use (e.g. plotting). The two orbital sets are stored in the same dump record and can be restored at later stages using
ORBITAL,record,[TYPE=]LOCAL or
ORBITAL,record,[TYPE=]PROJECTED, respectively.

DOMONLY=value

If value$\gt 0$ only domains are made, but no energy is computed. This can be used to check and save the domains for later use.

Parameters for selection of weak and distant pairs:

WEAKPAIR=distance

If all atoms of orbital domain [i] are separated by at least distance [a.u.] from any atom of orbital domain [j], pair (ij) is treated by MP2. The default is distance=1, which means that all pairs for which [i] and [j] have no atom in common are treated as weak pairs. Setting distance=0 eliminates weak pairs, i.e. all pairs are fully included in the calculation. This option has no effect for local MP2 calculations.

DISTPAIR=distance

If all atoms of orbital domain [i] are separated by at least distance [a.u.] from any atom of orbital domain [j], pair (ij) is treated approximately by MP2, provided the multipole approximation is activated. Setting distance=0 eliminates distant pairs, i.e. no pairs are treated approximately. Default is 0 (MULTP card: 8).

VERYDIST=distance

If all atoms of orbital domain [i] are separated by at least distance [a.u.] from any atom of orbital domain [j], pair (ij) is neglected. Setting distance=0 (default) eliminates very distant pairs, i.e. no pairs are neglected. Reasonable values for distance would be 12-15 [a.u.] Default is 0 (MULTP card: 15).

Parameters to define domains:

DOMSEL=value

Threshold for selecting the atoms contributing to orbital domains using the method of Boughton and Pulay. The default is value=0.98. value=1.0 would include all atoms into each orbital domain. The criterion is somewhat basis dependent. The larger the basis, the fewer functions will be selected with a given threshold. The default value usually works well for double-zeta basis sets. For larger basis sets (e.g., cc-pVTZ) it is recommended to use value=0.985. In most cases, the domain selection is uncritical for saturated molecules. However, for delocalized systems it is recommended to check the printed orbital domains! In cases of doubt, compare the domains you get with a smaller basis (e.g., cc-pVDZ). See also the MAXANG option below.

DELCOR=nshell

Activates elimination of basis functions corresponding to core orbitals. If nshell=1, only $1s$-functions are eliminated from projected space. If nshell=2 (default) $1s$ functions on first-row atoms, and $1s$, $2s$, and $2p$-functions are eliminated on second-row atoms. Nothing is eliminated on H or He atoms. If effective core potentials are used, nothing is deleted at the corresponding atom. Also, functions are only deleted if the norm of the projected function is below THRCOR (default 0.1)

DELBAS=ibaso

This parameter determines the method for eliminating redundant functions of pair domains.
ibaso=0: The space of normalized eigenvectors of ${\bf\tilde S}^{ij}$, which correspond to small eigenvalues, is eliminated (default if no gradients are computed).
ibaso $\gt$ 0: individual basis functions are eliminated. The value of ibaso affects details of the method to determine redundant functions.
ibaso=1: Redundant functions eliminated from pair domains, using Jacobi method for diagonalization of overlap matrices. This is the default if properties or gradients are computed.
ibaso=2: Redundant functions are eliminated from pair domains, using Householder method for diagonalization of overlap matrices.
ibaso=3: Redundant functions are eliminated from orbital and pair domains, using Jacobi method for diagonalization of overlap matrices.
ibaso=4: Redundant functions are eliminated from orbital and pair domains, using Householder method for diagonalization of overlap matrices.
The diagonalization method has only an effect for DELEIG=1 if degenerate eigenvalues are present. ibaso$\gt 2$ has only an effect if NONORM=0.

Parameters for selection of redundant functions if DELBAS$\gt 0$:

DELSHL=idlshl

This parameter determines if whole shells of basis functions (i.e., all $p$-functions for a given exponent at one atom) should be simultaneously eliminated. This may be useful in order to guarantee rotational invariance in geometry optimizations and frequency calculations.
idlshl=1: eliminate as many functions of a shell simultaneously as possible, but never more than determined by small eigenvalue of the overlap matrix (default).
idlshl=2: as idlshl=1, but also eliminate functions with identical norm simultaneously.
idlshl=3: eliminate all functions of a shell simultaneously, even if a larger number of functions is deleted than determined by small eigenvalues of the overlap matrix. This must be used with care, since very poor energies may sometimes result!
idlshl=4: as idlshl=3, but also eliminate functions with identical norm simultaneously.
idlshl$\gt 4$: as idlshl=4, but equivalent functions centred at all symmetry equivalent atoms are considered to form a shell (not recommended!).

TYPECHECK=typechk

If nonzero, activates basis function type restrictions in redundancy check. For a given atom, only basis functions corresponding to occupied atomic orbitals are allowed to be deleted. For instance, on first row atoms at most two $s$-functions and one $p$-shell will be deleted. No functions are deleted from hydrogen or He atoms.

DELEIG=idleig

This option determines how redundant basis functions are selected.
idleig=0: functions corresponding to the smallest diagonal elements of projected orbital matrix are eliminated.
idleig=1: Functions corresponding to the largest coefficients in the eigenvectors of ${\bf\tilde S}^{ij}$ are deleted (default). Since degenerate eigenvectors can arbitrarily mix, the selection may not be unique and depend on the diagonalization method (see DELBAS).

DELCMIN=value

Only effective with DELEIG=1. Only basis functions with coefficients larger than value in the eigenvectors of small eigenvalues can be deleted (default 0.1).

Parameters for multipole treatment of exchange operators

MULTMETHOD=option

Used internally by the MULTP card - don't mess with it.

DSTMLT=level

Determines the expansion level of the multipole expansion of distant pairs (e.g. 1 means dipole approximation, 2 quadrupole approximation and so on). Default is 0 (MULTP card: 3).

Parameters for energy partitioning:

IEPART=value

enables/disables energy partitioning.
iepart=0: energy partitioning is disabled.
iepart=1: energy partitioning is enabled.
iepart=2: energy partitioning is enabled. Additionally, a list of all pair energies and their components is printed.

EPART=cutoff

cutoff parameter to determine individual monomers in a cluster (i.e. centre groups). Should be somewhat larger than the largest intramolecular bond length (given in a.u.).

Miscellaneous options:

SKIPDIST=skipdist

Test-parameter. Its value should only affect the efficiency but not influence the results.
skipdist=-1: weak and distant pairs are set to zero after MP2 but are not eliminated from the pair list and not skipped in any loop.
skipdist=0: No pairs are deleted from pair list, but weak and distant pairs are skipped in the loops were appropriate.
skipdist=1: Very distant pairs are neglected from the beginning. Distant pairs are eliminated after MP2.
skipdist=2: As skipdist=1, but also weak pairs are eliminated after MP2.
skipdist=3: As skipdist=2, but distant pairs are eliminated from the operator list in case of LMP2 with multipole approximations for distant pairs. This is the default.

ASYDOM=jiterm

Enables the use of asymmetric domains for distant pairs. The asymmetric domain approximation supplements the multipole approximation for distant pairs, as it suppresses the treatment of configurations for which no integrals can be computed by multipole expansion. This leads to computational savings and improved numerical stability.
jiterm=0: Disable asymmetric domains.
jiterm=-1: Enable asymmetric domains (default).
jiterm=-2: Enable a variation of the asymmetric domain formalism: Exchange operators will initially be projected to the asymmetric domain instead of simply packed.

LOCSING=locsing

If locsing.ne.0, the single excitations use the full space, i.e., they are not treated locally. This is only works for LOCAL=1.

MAXANG=lmax

The purpose of this experimental option is to reduce the basis set sensitivity of the Boughton-Pulay (BP) method for domain selection. Only basis functions with angular momentum up to lmax-1 are included when computing the overlap of the approximate and exact orbitals. For example, MAXANG=2 means to omit all contributions of $d$, $f$ and higher angular momentum functions. To obtain reasonable domains, the value of DOMSEL must often be reduced (to 0.97 or so). This option should only be used with care!

MAXBP=maxbp

If maxbp=1, the atoms are ranked according to their contribution to the Boughton-Pulay overlap (default); this should normally give the smallest and best orbital domains. If maxbp=0, the atoms are ranked according to Mulliken charges. In both cases atoms with Mulliken charges greater than 0.6 are always included, and atoms with the same Mulliken charges are added as groups.

MULLIKEN=option

Determines method to determine atomic charges. option=0: diagonal elements of ${\bf S}^{\frac{1}{2}} {\bf C}$ are used. option=1: Mulliken gross

PIPEKAO=option

If option$\ge 0$, the orbitals are localized my maximizing the coefficients of basis functions of a given type at a given atom. Normally, this is only useful to uniquely define degenerate orbitals in atoms. For instance, when this option is used to localize the orbitals for a dimer like (Ar)$_2$ at a very long distance, clean $s$, $p_x$, $p_y$, and $p_z$ atomic orbitals will be obtained. It is not recommended to use this option for molecular calculations!

NONORM=value

Determines if projected functions are normalized (not recommended). value=-1: projected orbitals are normalized before redundancy check.
value=0: projected orbitals are normalized after redundancy check (default).
value=1: projected orbitals are normalized in redundancy check, afterwards unnormalized.
value=2: projected orbitals are never normalized.

LMP2ALGO=value

If nonzero, use low-order scaling method in LMP2 iterations. This may require more CPU time in calculations for smaller molecules.

OLDDEF=value

For compatibility with older versions: if nonzero, revert to old defaults. Options set before this may be overwritten.

Thresholds:

THRPIP=thresh

Threshold for Pipek-Mezey localization. The localization is assumed to be converged if all $2\times 2$ rotation angles are smaller then thresh. The default is $1.d-12$. It can also be modified globally using GTHRESH, LOCALI=thresh. Note that GTHRESH is not an input command of the local program and must be given before the METHOD card.

THRORB=thresh

Threshold for eliminating functions from pair domains whose norm is smaller then thresh after projecting out the occupied space. The default is throrb=1.d-6.

THRLOC=thresh

Threshold for eliminating redundant basis functions from pair domains. For each eigenvalue of ${\bf\tilde S}^{ij} \lt thresh$ one function is deleted. The default is 1.d-6. The method used for deleting functions depends on the parameters IDLEIG and IBASO.

THRMP2=thresh

Threshold for neglecting small fock matrix couplings in the LMP2 iterations (default 1.d-8). Specifying a larger threshold speeds up the iterations but may lead to small errors in the energy. In the initial iterations, a larger threshold is chosen automatically. It is gradually reduced to the specified final value during the iterations.

THRCOR=thresh

Threshold for deleting projected core orbitals. The functions are only deleted if their norm is smaller than thresh (default 0.1)

The thresholds can also be specified on the THRESH card.