Howdy!
I have been doing some geometry optimization calculations using TCE CCSD(T) of NWChem 6.3. I am puzzled by different optimized energy and geometry between using DFT and SCF reference wave functions (RWF) for CCSD(T) calculations.
With DFT RWF
----------------------
Optimization converged
----------------------
Step Energy Delta E Gmax Grms Xrms Xmax Walltime
---- ---------------- -------- -------- -------- -------- -------- --------
@ 3 -1.21194125 -1.7D-07 0.00004 0.00004 0.00007 0.00012 57.8
ok ok ok ok
Z-matrix (user)
--------
Units are Angstrom for bonds and degrees for angles
Type Name I J K L M Value Gradient
----------- -------- ----- ----- ----- ----- ----- ---------- ----------
1 Stretch 2 1 0.75972 0.00004
With SCF RWF
----------------------
Optimization converged
----------------------
Step Energy Delta E Gmax Grms Xrms Xmax Walltime
---- ---------------- -------- -------- -------- -------- -------- --------
@ 3 -1.17245645 1.7D-10 0.00000 0.00000 0.00006 0.00011 17.7
ok ok ok ok
Z-matrix (user)
--------
Units are Angstrom for bonds and degrees for angles
Type Name I J K L M Value Gradient
----------- -------- ----- ----- ----- ----- ----- ---------- ----------
1 Stretch 2 1 0.74265 -0.00000
Here are my inputs.
With DFT RWF
start h2-ccsd
echo
charge 0
geometry units angstroms
symmetry C1
zmat
H
H 1 0.80
end
zcoord
cvr_scaling 1.2
end
end
dft
odft
mult 1
vectors input atomic output h2.movecs
xc m06
iterations 200
end
TCE
DFT
CCSD(T)
FREEZE core
END
driver
maxiter 80
end
basis "ao basis" cartesian print
END
task TCE optimize
With SCF RWF
start h2-ccsd
echo
charge 0
geometry units angstroms
symmetry C1
zmat
H
H 1 0.80
end
zcoord
cvr_scaling 1.2
end
end
SCF
SINGLET
UHF
vectors input atomic output h2.movecs
END
TCE
SCF
CCSD(T)
FREEZE core
END
driver
maxiter 80
end
basis "ao basis" cartesian print
END
task TCE optimize
Thanks
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