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32.5 General Options

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 (obsolete).
LOCAL=4: Fully local calculation (default). This is the fastest method for large molecules with many weak pairs and requires minimum memory.

LOCORB=option
If this option is given and option$>0$, 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 directive and LOCALI command). In the latter case, the most recent localized orbitals are used. Setting option=-1 switches the localization off. If option$> 1$ the localized orbitals are printed. Note: Boys localization can only be performed using the LOCALI command. The program will use the Boys orbitals if they are found in the orbital record and the LOCORB option is absent or option$\le 0$.

LOC_METHOD=method
This option allows to select between Pipek-Mezey (method=PM) or Natural Orbitals (method=NBO) localization. If Pipek-Mezey orbitals are requested, the default Boughton-Pulay domain selection will be used. When method=NBO, the domain selection will be based on the NPA charges, with NPASEL=0.03 (by default). In both cases, the domain selection parameter can be explicitly given (cf. DOMSEL and NPASEL options) in order to use another domain criterion. If localized orbitals are found in the orbital record, but the type does not coincide, the orbitals are again localized according to method and used in the calculation.

SAVORB=record
Allows the localized and projected orbitals to be saved in 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$>0$ only domains are made, but no energy is computed. This can be used to check and save the domains for later use.

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). The default for MULTP is 3.

INTERACT
Automatically determine individual molecules in a calculation and set appropriate pair lists for computing interaction energies. See section 32.9.8 for more details.

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
Experimental test parameter. 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 THRBP must often be reduced (to 0.97 or so). This option should only be used with care!

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 (default in gradient calculations).

LMP2ALGO=value
If nonzero, use low-order scaling method in LMP2 iterations. Values can be 1, 2, or 3, and 3 is usually fastest if large basis sets are used.

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 than thresh. The default is $1.d-12$. It can also be modified globally using GTHRESH, LOCALI=thresh.

THRORB=thresh
Threshold for eliminating functions from pair domains whose norm is smaller than 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 ${\bf\tilde S}^{ij} <thresh$ 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 directive.



Next: 32.6 Options for selection Up: 32 LOCAL CORRELATION TREATMENTS Previous: 32.4 Summary of directives   Contents   Index   PDF

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