| 9:38:51 AM PST - Wed, Dec 10th 2014 |
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Quote: Feb 1st 3:31 pmHi,
Do I understand correctly that MBPT4 is equivalent to MP4 for the ground state?
So, can I change the code
mp2
tight
freeze atomic
end
task MP2 optimize
to
TCE
MBPT4
freeze atomic
end
task TCE optimize
for geometry optimization, taking into account the MP4 correlation?
Yes, and you can use both MP4 and MBPT4 as input keywords with TCE. If you have a closed-shells system, please use "mbpt4sdq(t)" instead, as this implementation is significantly more efficient than the default "mbpt4" one.
In case you are curious, it is named this way because the implementation corresponds to solving MP4(SDQ) iteratively (without storing the quadruples amplitudes) and then adding the triples terms, (T), obtained via the CCSD(T) code. It's absolutely correct for closed-shell systems with canonical orbitals. Not sure about ROHF or UHF.
Jeff
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