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20.2. FORMAT OF KEYWORDS AND COMMENTS
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The ansatz flag determines which ansatz is used to calculate the RIMP2-F12 ground state energy.
(Ansatz 2 is used if ansatz is absent.)
r12model char
char =A, A’ or B
The r12model flag determines which approximation model is used to
calculate the RI-MP2-F12 ground state energy.
(Ansatz B is used if r12model is absent.)
comaprox char
char =F+K or T+V
The comaprox flag determines the method used to approximate the commutator integrals [T, f12 ].
(Approximation T+V is used if comaprox is absent.)
cabs char val
char =svd or cho
The cabs flag determines the method used to orthogonalize the orbitals
of the CABS basis. val is the threshold below which CABS orbitals are
removed from the calculation.
(svd 1.0d-08 is used if cabs is absent.)
examp char
char =noinv, fixed or inv with flip or noflip
The examp flag determines which methods are used to determine the
F12 amplitudes. For inv the amplitudes are optimized using the orbitalinvariant method. For fixed and noinv only the diagonal amplitudes
are non-zero and are either predetermined using the coalescence conditions (fixed), or optimized (noinv—not orbital invariant). If char =inv,
the F12 energy contribution is computed using all three methods. For
open-shell calculations noflip supresses the use of spin-flipped geminal
functions.
(The fixed flip method is used if examp is absent.)
pairenergy char
char =off or on
If char =off (default), the print out of the standard and F12 contributions to the pair energies is suppressed. The summary of the RI-MP2-F12
correlation energies is always printed out.
corrfac char
char =LCG or R12