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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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neo-scf calculations
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Cannot get rid of Imaginary Frequency
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3 93 November 25, 2025
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How To
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Webinar 83: Coupled Cluster Developments in Q-Chem
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2 68 November 19, 2025
Trouble using EOM-CCSD, with frozen core
Questions
6 102 November 19, 2025
Issue with S₁ State Optimization Under PCM – SCF Convergence Error
Questions
3 88 November 18, 2025
How to set broken‑symmetry state?
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7 132 November 17, 2025
Problem oxygen potential energy scan using CCSD(T) and EA state PES using EA-EOM-CCSD
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11 492 November 11, 2025
“double free or corruption (out)” error in TDDFT + EFP job with large number of fragments
Questions
1 116 November 9, 2025
Cannot escape an imaginary frequency
Questions
1 153 November 7, 2025
Limited support for analytic Hessians in Q-Chem
Questions
10 875 November 6, 2025
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Questions
1 148 November 1, 2025
TSVDW and MBD crashes
Questions
1 143 October 30, 2025
Unexpected behaviour: core orbitals are not frozen during MP2/MP3 step in ADC calculations
Questions
4 286 October 27, 2025
SCF convergence issue with diffuse functions on basis set
Questions
27 527 October 22, 2025
Crash upon frequency calculations with range separated bybrid
Questions
1 230 October 21, 2025
Cryptic import_xcfunc warning
Questions
10 361 October 20, 2025
What sort of RI techniques are safe to use with different types of SCF?
Questions
3 263 October 16, 2025
RI worsens SCF timings
Questions
4 284 October 16, 2025