Release Log for Q-Chem 6.4

Q-Chem 6.4.0 Release

December 8, 2025

Changes to keywords and default behavior:

  • USE_LIBQINTS=0 is now forced for calculations with a multipole section (Kaushik Nanda)

General features and improvements:

  • Stochastic RI-CC2 analytical gradients and derivative coupling (Chongxiao Zhao, Wenjie Dou, Chenyang Li, Joonho Lee, Qi Ou)
  • Added two-step Cholesky decomposition and its corresponding gradient (Tingting Zhao, Anna Krylov)
  • Performance improvements for libqints-based kernels (Xintian Feng)
  • libqch5 for output parsing (Andrew Gilbert, Aitor Diaz Andres, David Casanova)
  • Resolved issues with:
    • Failure to print orbitals for systems with more than 1000 atoms (John Herbert)
    • Memory allocation error when calculating restricted LDA explicit nuclear Hessian (Xintian Feng)
    • Incorrect results for partial Hessian calculations using finite difference of gradients (Kaushik Nanda)
    • Incorrect results for multipole field when using new libqints integral driver (Kaushik Nanda)
    • Fix a bug from last JK engine API change (Xintian Feng)

Density functional theory and self-consistent field:

  • Upgrade DFT-D4 (Kuan-Yu Liu)
  • B97-type functionals in TAO-DFT (TAO-B97-D4, TAO-B97X-D4, TAO-wB97X-D4 and KS-wB97X-D4) (Shaozhi Li, Jeng-Da Chai)
  • New DFT functionals: B97MV-D3s(BJ), B97MV-D4, wB97MV-D4, wB97MV-D3s(BJ), wB97XV-D3s(BJ), wB97XV-D4, Pr2SCAN69-D4, Pr2SCAN50-D4, wPr2SCAN50-D4, revDOD-PBEP86-D4, revDSD-PBEP86-D4, xDSD75-PBEP86-D4, wDSD72-PBEP86-D4, B2NC-PLYP, mPW2-PLYP, mPW2NC-PLYP, SOS0-PBE0-2 (Xintian Feng)
  • New DeltaSCF driver with new, easier interface for DeltaSCF calculations, including restricted open-shell and unrestricted triplet SCF calculations, ROKS and unrestricted spin symmetry-broken SCF calculations, overlaps and transition dipole moments between singlet and ground state, overlaps between SOMOs and final states, and generation of cube files for SOMOs. (Juan Arias)
  • PBEh-3c and HF-3c Seminumerical Analytic Frequency, 5-point stencil for semi empirical part (Avik Ojha, John Herbert)
  • Enabled TRANS_MOM_SAVE (saving SCF orbitals for computing transition dipole moments) for restricted SCF (Juan E. Arias Martinez)
  • Enabled RESET_INCFOCK for calculations using gen_scfman (Xintian Feng)
  • Disabled MBD when BASIS2 is used (John Herbert)

Correlated methods:

  • Implemented the core-valence separation (CVS) approximation for ROCIS, XCIS and QROCIS (Avik Ojha, John Herbert)
  • MRSF-TDDFT energy (Arnab Chakraborty, Zheng Pei, Yihan Shao, Anna Krylov)
  • Adding inner-valence projection option to EOM-IP/EE-CCSD solvers (Wojtek Skomorowski)
  • Resolved issues with:
    • Incorrect results in EOM-DEA/DIP-CCSD gradient calculations when CC_BACKEND=XM (Tingting Zhao, Anna Krylov)
    • Resolved error when combining RAS_PT2 rem variable with RAS_PRINT = 2 (Abel Carreras, David Casanova)
    • Crash in VCD calculation due to REM variable overlap

Incorporation of quantum nuclear effects (NEO suite):

  • NEO-CC2 method for modeling excited states (Jonathan Fetherolf, Sharon Hammes-Schiffer)
  • Added NEO-CCSD(T), NEO-CCSDTeep,epp methods (Rowan Goudy, Sharon Hammes-Schiffer)
  • Added frozen core approximation to libneo (Rowan Goudy, Sharon Hammes-Schiffer)
  • Enabled NEO-CC geometry optimization with finite-difference gradients (Rowan Goudy, Sharon Hammes-Schiffer)

Molecular dynamics, non-adiabatic dynamics, embedding, and solvation:

  • Added iterative CC-in-DFT embedding approach for property calculations (Anthuan Ferino Pérez, Thomas Jagau)
  • Generalization of possible spin state configurations in the projection-based embedding module (Elena Kolodzeiski, Christopher J. Stein)

Fragment and energy decomposition analysis:

  • Resolved issues with:
    • Printing of EDA-related warning for external charges in non-EDA calculations (John Herbert)
    • Integer overflow problem in some QM/MM PCM calculations (Kaushik Nanda)

Previous Release Logs

 

Request A Demo!