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Report SCF (HF/DFT) Convergence Issues
Questions

Dear Q-Chem Community, If you have any SCF (HF/DFT) jobs that are time-consuming or are facing convergence difficulties with Q-Chem, please send them to support@q-chem.com with the subject line “SCF Convergence Issue” t…

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Strange outcome in RAS-SF calculation
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Speeding up ADC(2) calculations
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SOC for unrestricted TDDFT
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Optimal settings for large DFT calculations
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3 487 February 28, 2026
Using FRAGMO with ptSS-PCM and CDFT for Vertical Electron Transfer Calculation
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3 94 February 26, 2026
Geometry Optimization with SS_PCM
Questions
1 99 February 25, 2026
Thresh/s2thresh 14?
Questions
8 122 February 24, 2026
Normal Modes Question
Questions
3 255 February 23, 2026
Symmetry in CCSD(T) frequency calculation
Questions
4 130 February 23, 2026
Symmetry of EOM-EA-CCSD. Significance?
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1 139 February 21, 2026
Units of vibrational eigenvectors
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2 158 February 20, 2026
EOM-EA-CCSD on a Excited state
Questions
1 110 February 20, 2026
ROKS emission energy with nonequilibrium solvent
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0 100 February 20, 2026
Dyson orbital using EOMCCSDT-IP
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1 128 February 20, 2026
Frequency calculation speedup
Questions
1 241 February 19, 2026
What is the correct input for the GEOM_OPT_MODE
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2 144 February 19, 2026
Large number of imaginary frequencies with ROKS and delta SCF
Questions
1 112 February 19, 2026
Ehrenfest Molecular Dynamics
Questions
2 119 February 19, 2026
S1 Geom optimization based on TDDFT and delta SCF approach
Questions
11 213 February 18, 2026
Q-Chem license on new MacOS
How To
0 135 February 17, 2026
Stuck CCSD frequency calculation
Questions
2 147 February 16, 2026
Issue with designing functionals
Questions
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COSMO input file
Questions
2 137 February 13, 2026