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Questions tagged [mrcc]

For questions about (or involving) the MRCC electronic structure software package.

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23 votes
3 answers
783 views

What is the largest system that has been studied by the coupled cluster method?

This is parallel to the analogous question about the largest DFT calculation: What is the largest material that has been studied using density functional theory? I assume we allow high performance ...
Paulie Bao's user avatar
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17 votes
3 answers
937 views

How is "basis set projection" done?

I recently came across something called the basis set projection in Q-chem's manual. What it seems to do is to take the converged SCF in a smaller basis set, and then "projects" that onto a ...
S R Maiti's user avatar
  • 7,021
16 votes
3 answers
1k views

How to calculate homolytic bond dissociation energies?

An experimental colleague asked me how hard it would be to calculate homolytic bond-dissociation energies for different phosphonates which are involved in a Hydrophosphination. The compounds include ...
Cody Aldaz's user avatar
  • 8,017
11 votes
2 answers
1k views

Analytic gradient for DLPNO-CCSD

Is there a formula for analytical gradients (for geometry optimization) for the DLPNO-CCSD method? I ask because I know that it is not implemented in ORCA. Maybe PNO-CCSD is implemented in MRCC or ...
Paulie Bao's user avatar
  • 3,973
10 votes
2 answers
2k views

What are Pair Natural Orbitals?

Recently, I came across electron correlation methods that use local pair natural orbitals (LPNOs) or domain-based local pair natural orbitals (DLPNO), such as DLPNO-MP2, DLPNO-CCSD etc. The dynamic ...
S R Maiti's user avatar
  • 7,021
8 votes
1 answer
238 views

Interfacing MRCC with CFOUR for dynamic polarizability

I have asked this question on the MRCC forum but did not get an answer. I am trying to understand how to use CFOUR with the MRCC program for computing dynamic polarizability. To begin with, I am ...
ankit7540's user avatar
  • 275
6 votes
1 answer
189 views

Using the same input (MINP) file, why does MRCC fail with a "normal" fort.55 file, but succeeds with a longer fort.55 file that has duplicate entries?

I have the following fort.55 file: ...
Jaafar Mehrez's user avatar
5 votes
1 answer
31 views

ssr functional for the dft=userd in MRCC package

I found the nice userd example with the standard functional in the latest MRCC manual but I wonder if one can also use ssr (...
nesquik91's user avatar
5 votes
0 answers
28 views

Core-valence separation (CVS) keyword in MRCC program [closed]

I am interested in using the CVS option in CI calculations to get core-excited states. I tried to use the MRCC program which possesses this option according to the manual (cvs=...). I performed some ...
EvGeniy's user avatar
  • 371
4 votes
1 answer
203 views

Which programs can calculate corrections to the Born-Oppenheimer approximation?

I need to calculate the electric dipole moment of molecules like HD, in which the electric dipole moment is zero in the Born-Oppenheimer approximation (meaning that it's absolutely necessary to ...
Patrick's user avatar
  • 41
4 votes
1 answer
131 views

Crash of DF-CCSD or DF-CCSD(T) geometry optimization (MRCC package)

I am interested in geometry optimization at the CCSD(T) or DF-CCSD(T) level, with MRCC. The calculation, however, crashes when executing prop: ...
EvGeniy's user avatar
  • 371
2 votes
1 answer
49 views

MRCC/CFOUR interface bug for a single atom calculation?

I am trying to run the calculation of the DBOC using CFOUR/MRCC interface for a single atom. The calculation runs with no issues without MRCC (i.e. if CC_PROG=MRCC is removed from the ZMAT file below),...
Roman Korol's user avatar
  • 1,073