$CCHEMRI group (optional, relevant if CODE=RICCHEM in $MP2)
This group controls how the RI-MP2/RI-ZAPT energy
and RI-MP2 gradient are performed.
IAUXBF = 0 uses Cartesian Gaussians
= 1 uses spherical harmonics
for the auxiliary basis set used to expand the
MP2 energy expression into products of 3-index
matrices. The default is inherited from ISPHER
The following options are for the RI-MP2 gradient only:
INVCUT = specifies which eigenvectors from the two-
center ERI matrix are used to constuct the
inverted Coulomb metric (default 10).
Eigenvectors with eigenvalues that have a
magnitude less than INVCUT
are not used to contruct the Coulomb metric.
Decreasing INVCUT(e.g. INVCUT=7) can help with
numerical issues.
IRTCUT = specifies which eigenvectors from the block
diagonal relaxed two-particle density matrix
are used to contruct the square root of said
matrix. Eigenvectors with eigenvalues that have
a magnitude less than IRTCUT
are not used to contruct the matrix root.
This matrix is used to construct part of
the lagrangian matrix (default 10).
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Edited by Shiro KOSEKI on Thu Mar 5 10:25:38 2020.