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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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Partial frozen scan
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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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Cannot get rid of Imaginary Frequency
Questions
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TDA with RSH giving negative triplet excitation
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“ADC(3) singlet and triplet excited states with PCM – input and disk quota issues”
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How To
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1 85 November 20, 2025
Webinar 83: Coupled Cluster Developments in Q-Chem
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Trouble using EOM-CCSD, with frozen core
Questions
6 113 November 19, 2025
Issue with S₁ State Optimization Under PCM – SCF Convergence Error
Questions
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Problem oxygen potential energy scan using CCSD(T) and EA state PES using EA-EOM-CCSD
Questions
11 516 November 11, 2025
“double free or corruption (out)” error in TDDFT + EFP job with large number of fragments
Questions
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Cannot escape an imaginary frequency
Questions
1 166 November 7, 2025
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Questions
10 896 November 6, 2025
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Questions
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TSVDW and MBD crashes
Questions
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Unexpected behaviour: core orbitals are not frozen during MP2/MP3 step in ADC calculations
Questions
4 302 October 27, 2025
SCF convergence issue with diffuse functions on basis set
Questions
27 548 October 22, 2025
Crash upon frequency calculations with range separated bybrid
Questions
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Cryptic import_xcfunc warning
Questions
10 375 October 20, 2025