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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…

3 1094 November 22, 2024
Possible issue with linear dependencies in the basis when calculating dynamic polarizabilities
Questions
2 24 December 17, 2025
downloading and installing qcIntel version 6402
Questions
1 20 December 17, 2025
Discrepancies between RIMP2 polarizabilities with FDIF = 0 and FDIF = 1
Questions
1 45 December 12, 2025
Excitation energy transfer between two carotinoids
Questions
3 50 December 12, 2025
Machine learned PES
Questions
1 96 December 1, 2025
Partial frozen scan
Questions
3 101 November 29, 2025
Dipole Moments with MBD dispersion
Questions
1 80 November 28, 2025
Correlation consistent basis sets and effective core potentials should be included?
Questions
1 114 November 28, 2025
vdW-TS (MBDVDW) vibrational frequencies
Questions
15 119 November 27, 2025
neo-scf calculations
Questions
1 69 November 25, 2025
aug-cc-pV(n+d)Z basis sets
Questions
1 74 November 25, 2025
Cannot get rid of Imaginary Frequency
Questions
3 119 November 25, 2025
TDA with RSH giving negative triplet excitation
Questions
11 171 November 24, 2025
“ADC(3) singlet and triplet excited states with PCM – input and disk quota issues”
Questions
3 359 November 21, 2025
Second Derivative for DC-DFT
How To
9 283 November 21, 2025
TD-DFT geometry optimization using IEFPCM solvation model
Questions
1 94 November 20, 2025
Webinar 83: Coupled Cluster Developments in Q-Chem
Webinars
0 87 November 20, 2025
Obtaining cube file for mo's, suggesting bond breaking
Questions
2 81 November 19, 2025
Trouble using EOM-CCSD, with frozen core
Questions
6 116 November 19, 2025
Issue with S₁ State Optimization Under PCM – SCF Convergence Error
Questions
3 107 November 18, 2025
How to set broken‑symmetry state?
Questions
7 151 November 17, 2025
Problem oxygen potential energy scan using CCSD(T) and EA state PES using EA-EOM-CCSD
Questions
11 531 November 11, 2025
“double free or corruption (out)” error in TDDFT + EFP job with large number of fragments
Questions
1 128 November 9, 2025
Cannot escape an imaginary frequency
Questions
1 171 November 7, 2025
Limited support for analytic Hessians in Q-Chem
Questions
10 905 November 6, 2025
How does IQmol calculate the center of mass of a molecule?
Questions
1 165 November 1, 2025
TSVDW and MBD crashes
Questions
1 156 October 30, 2025
Unexpected behaviour: core orbitals are not frozen during MP2/MP3 step in ADC calculations
Questions
4 308 October 27, 2025
SCF convergence issue with diffuse functions on basis set
Questions
27 565 October 22, 2025