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Problem running XMCQDPT2 calculation with large (16e,16o) active space

Martial Boggio-Pasqua

I have been using Firefly recently to run CASSCF and XMCQDPT2 calculations on a medium-sized organic photochromic system. This system requires a large active space: (14e,14o) to study its absorption properties and (16e,16o) to study its photoswitching mechanism. While I have been able to run XMCQDPT2 with a (14e,14o) active space, I am not able to run a similar job with a (16e,16o) active space. I cannot circumvent the memory limit in mwords. I get the following error message in MQCACI: ERROR: MEMORY REQUEST EXCEEDS MAXIMUM. 729888763 WORDS REQUIRED    460000000 AVAILABLE.

Maybe someone can tell me if this calculation is possible or not. I have enclosed an input file in which the CASSCF(16,16) part is skipped as the CASSCF orbitals have been saved in a previous job.

I would be extremely grateful if I can get some assistance with this issue as the whole series of calculations I am planning to perform require this large (16e,16o) active space.

I am using the 8.2.0 version.

Many thanks in advance!

This message contains the 4923 kb attachment
[ boggio_xmcqd16pt2_vtz_input.tar.gz ] Complet input file and external basis set file

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