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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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Machine learned PES
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Partial frozen scan
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Dipole Moments with MBD dispersion
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Correlation consistent basis sets and effective core potentials should be included?
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vdW-TS (MBDVDW) vibrational frequencies
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15 81 November 27, 2025
neo-scf calculations
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1 49 November 25, 2025
aug-cc-pV(n+d)Z basis sets
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1 55 November 25, 2025
Cannot get rid of Imaginary Frequency
Questions
3 90 November 25, 2025
TDA with RSH giving negative triplet excitation
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11 143 November 24, 2025
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3 335 November 21, 2025
Second Derivative for DC-DFT
How To
9 238 November 21, 2025
TD-DFT geometry optimization using IEFPCM solvation model
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1 71 November 20, 2025
Webinar 83: Coupled Cluster Developments in Q-Chem
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Obtaining cube file for mo's, suggesting bond breaking
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2 65 November 19, 2025
Trouble using EOM-CCSD, with frozen core
Questions
6 99 November 19, 2025
Issue with S₁ State Optimization Under PCM – SCF Convergence Error
Questions
3 83 November 18, 2025
How to set broken‑symmetry state?
Questions
7 129 November 17, 2025
Problem oxygen potential energy scan using CCSD(T) and EA state PES using EA-EOM-CCSD
Questions
11 487 November 11, 2025
“double free or corruption (out)” error in TDDFT + EFP job with large number of fragments
Questions
1 114 November 9, 2025
Cannot escape an imaginary frequency
Questions
1 150 November 7, 2025
Limited support for analytic Hessians in Q-Chem
Questions
10 871 November 6, 2025
How does IQmol calculate the center of mass of a molecule?
Questions
1 144 November 1, 2025
TSVDW and MBD crashes
Questions
1 140 October 30, 2025
Unexpected behaviour: core orbitals are not frozen during MP2/MP3 step in ADC calculations
Questions
4 283 October 27, 2025
SCF convergence issue with diffuse functions on basis set
Questions
27 523 October 22, 2025
Crash upon frequency calculations with range separated bybrid
Questions
1 226 October 21, 2025
Cryptic import_xcfunc warning
Questions
10 358 October 20, 2025
What sort of RI techniques are safe to use with different types of SCF?
Questions
3 260 October 16, 2025
RI worsens SCF timings
Questions
4 280 October 16, 2025