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31.6 Options

There are many options available, but these are hardly needed. Normally, when standard orbital basis sets such as aug-cc-PVTZ or VTZ-F12 are used, appropriate defaults are used and no further options are needed. A typical input simply reads

basis=vtz-f12
hf
ccsd(t)-f12

We recommend to specify options only when necessary and when it is well understood what they mean!

Options for canonical and local versions:

DF_BASIS=basis

Select the basis for density fitting (see section 15 for details). basis can either refer to a set name defined in the basis block, or to a default MP2 fitting basis (e.g., DF_BASIS=VTZ generates the VTZ/MP2FIT basis). By default, the MP2FIT basis that corresponds to the orbital basis is used.

DF_BASIS_EXCH=basis

Select the density fitting basis for computing the exchange and Fock operators. By default, the JKFIT basis sets which correspond to the orbital basis are used.

RI_BASIS=basis

Select the basis for the resolution of the identity (RI). This can refer to a default basis set or a set name defined in a basis block. For F12 methods the Hartree-Fock JKFIT basis sets perform well for the RI, despite having been optimized for other purposes. These sets are used by default for the AVnZ orbital basis sets. The basis type can be appended to the basis name after a slash, e.g.
RI_BASIS=AVQZ/JKFIT would use the specified JKFIT set, or RI_BASIS=AVQZ/OPTRI would use the optimized CABS basis sets of Peterson et al. These are recommended for the AVnZ and VnZ-F12 basis sets and used by default for the latter ones. Note that each OPTRI basis is associated to a specific orbital basis. Therefore, the name of the OPTRI basis must either be the same as that of the orbital basis, or be omitted, e.g., RI_BASIS=OPTRI selects automatically the correct set for the current orbital basis.

In case of R12-methods (which are not recommended to be used), the RI basis should be chosen to be a large uncontracted AO basis (at least AVQZ). Contraction/uncontraction can be forced appending (CONTRACT) or (UNCONTRACT) to the basis name, e.g.,
RI_BASIS=AVQZ(UNCONTRACT)/ORBITAL. If other options are given in parenthesis, these can be separated by commas, e.g.,
RI_BASIS=AVQZ(f/d,UNCONTRACT)/ORBITAL.
Alternative forms, which should work as well, are
RI_BASIS=AVQZ(f/d)(UNCONTRACT)/ORBITAL
or
RI_BASIS=AVQZ(f/d)/ORBITAL(UNCONTRACT).
Note that the CONTRACT/UNCONTRACT option cannot be used with basis set names previously defined in a basis block.

CONTEXT=context

Can be used to change the default type for the RI basis, e.g. CONTEXT=OPTRI will use the OPTRI basis sets that correspond to the VnZ-F12 or AVnZ basis sets.

ANSATZ=ansatz

Select the explicitly correlated ansatz ansatz methods. See section 31.7 for the possibilities and further details.

GEM_BASIS

Basis set name for geminal expansion; atom labels are ignored. This can either be OPTFULL (full nonlinear fit of the geminal expansion), EVEN (even tempered fit), or refer to a set name defined in a previous BASIS block. Default is OPTFULL.

GEM_TYPE

Frozen geminal type: LINEAR or SLATER, default is SLATER.

GEM_NUMBER

Number of Gaussian geminal functions (default 6).

GEM_CENTRE

Centre of even tempered geminal exponents, if GEM_BASIS=EVEN (default 1.0).

GEM_RATIO

Ratio of even tempered geminal exponents, if GEM_BASIS=EVEN (default 3.0).

GEM_BETA

Exponent for Slater-type frozen geminal, or parameter for weight function in other frozen geminal models (default 1.0 $a_0^{-1}$). It is possible to specify extra exponents for core-core and core-valence correlation. If two values are given (in square brackets), the first is used for valence pairs, the second for core-core (cc) and core-valence (cv) pairs. If three values are given, the first is used for vv, the second for cv, and the third for cc correlation.

GEM_OMEGA

Exponent for weighting function (default -1, which means a value derived from GEM_BETA).

GEM_MOM

Exponent for r in omega fitting (default 0).

GEM_M

Exponent for r in weighting function (default 0).

GEM_MAXIT

Max. number of iterations in geminal optimization (default 200).

GEM_PRINT

Print parameter for geminal optimization (default 0).

GEM_DEBUG

Debug option for geminal optimization (default 0).

GEM_ACC

Convergence threshold for geminal line search (default 0.001).

GEM_FAC

Scaling factor for exponents in geminal optimization (default 1.0).

GEM_METHOD

Geminal optimization method (augmented Hessian (AH) or Newton-Raphson (NR), default AH).

GEM_TRUST

Trust ratio in AH geminal optimization (default 0.4).

GEM_SHIFT

Hessian shift in AH geminal optimization (default 0).

GEM_NUMERICAL

Flags numerical integration in geminal optimization (default 0).

GEM_PLOT

Geminal plot file (default blank).

GEM_OPT_FULL

If nonzero (default), fit each geminal independently to Gaussians (if several exponents are used). If zero, the first exponent is fitted, unless GEM_BETA_OPT is specified.

GEM_BETA_OPT

Exponent used to fit the Gaussian expansion.

SIM_MULTGEM

Only for calculation with multiple exponents: if nonzero, loop externally over integral program for different exponents. This is implied automatically if each geminal is fitted independently. If the same Gaussian exponents are used for each Slater exponent, SIM_MULTGEM=0 can be used (default). In this case the integral program handles the general contractions (slightly faster).

PRINT=ipri

Select output level:

ipri=0

Standard output

ipri=1

Standard output plus more detailed information about integral evaluations.

ipri=2

Debugging output

THRBINV

Threshold below which non-physical eigenvalues are projected from approximate B matrices

THRF12

Threshold for integral screening contribution.

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