CC of excited B1 open-shell singlet of MgNe

Dear All,
I am carrying out preliminary CC calculation on MgNe using MRCC 25.1.4.
Everything went ok for the X 1_SIGMA_+ ground state and the A 3_PI_0 states (I calculated B1 and B2 triplets, both belong to the PI irrep in Cxv)
Then I tried the C 1_PI states (both B1 and B2): the UHf calculation seems ok, but right at the start of the CCSDT calculation I got and "Invalid spatial symmetry!" error message.
I also noticed that the UHF expectation value of S^2 = 1.0001, which does not seem a good omen.
I attach the input and output files.
Thank you in advance for any help.
Best,
Alessandro


INPUT
#
calc=CCSDT
core=2
basis=aug-cc-pVTZ
scftype=uhf
symm=B1
occ=7,2,2,0/6,3,2,0
mem=3000MB
ccprog=mrcc
cctol=10
scftol=14
scfdtol=14
itol=15

tprint=0.01
verbosity=3

charge=0
mult=1
unit=angs
geom
Mg
Ne 1 R

R=3.15

 

Dear Alessandro,
It is not possible to converge the CC equations to an excited state. Please use linear response CC starting from the ground-state CC solutions.

Dear Mihaly,
thanks for the suggestion, I'll try with LR-CC.
Best,
Alessandro

Dear Mihaly,
I followed your suggestion and managed to calculate the excited B1 open shell singlet of MgNe at the CCSDT/aug-cc-pVTZ level..
I plan to calculate the rotovibrational spectra of MgNe so I need well-converged energies (down to 1e-9 hartree).
As you can see in the attached plot,  I managed to reach such threshold for the CCSDT energy of the ground state A1 singlet but I was enable to do so for the excited B1 open-shell singlet.
Therefore, I would like to ask you:
1 - Which option should I use to increase the maximum number of LRCCSDT iterations? (ccmaxit does not affect LRCCSDT iterations)
2 - Have you any suggestion on how to increase the convergence rate of LRCCSDT?

I also attach the input and output files.

Thank you for your kind help
Best,
Alessandro

Dear Alessandro,
1) Unfortunately, currently the only way to change the max. number of iterations is to change the value of variable maxit in file MRCCCOMMON and then to recompile the code.
2) You can restart the LR-CCSDT calculation from the converged LR-CCSD coefficients, see the description of keyword rest in the manual.