Release Log for Q-Chem 6.3

Q-Chem 6.3.0 Release

May 22, 2025

Changes to keywords and default behavior:

Use MDQ-uFERF as default for EDA2 jobs ( EDA_UFERF = TRUE) (Hengyuan Shen, Abdulrahman Aldossary, Martin Head-Gordon)
Add REM control option for fragment CPSCF max iterations ( FRAG_CPSCF_MAXITER) (Yuezhi Mao)
Change alpha in BW-s2 jobs to n/1000 rather than n/100 (Linus Dittmer, Nikolay V. Tkachenko, Martin Head-Gordon)
Make O-V projection the default for basis2 calculations (BASISPROJTYPE = OVPROJECTION) (Kuan-Yu Liu)
All NEO jobs will now use a tight initial guess by default (Mathew Chow, Sharon Hammes-Schiffer)
Use nuclear core guess by default for NEO jobs with ghost atoms (Mathew Chow, Sharon Hammes-Schiffer)
Use simultaneous SCF by default for NEO calculations (NEO_SIMULTANEOUS_SCF = TRUE) (Mathew Chow, Sharon Hammes-Schiffer)
See a more detailed list of printing and default changes that could potentially affect scripts and parsers here.

General features and improvements:

MPI parallelization for finite-difference and many-body expansion calculations
Added torsional and flat-bottom potential restraints for geometry optimizations (Chance W. Lander, Yihan Shao)
Added bond stretch, r12pr34, angle, 1 to midpoint of 2 atoms, 1 to COM, and dihedral restraints to list of available restrained PES scan options (Chance W. Lander, Yihan Shao)
Re-enabled NTOs for RPAs, corrected to use proper particle and hole density matrices (John Herbert)
Resolved issues with:
- Hessian calculation rerun unnecessarily when GEOM_OPT_HESSIAN = READ in libopt3 (Yuezhi Mao)
- Remove bottlenecks in electronic JK gradient evaluation in libneo and librtneo (Mathew Chow, Sharon Hammes-Schiffer)
- Eliminate NaN values in Feshbach-Fano calculations for large, diffuse basis sets (Saikat Roy, Wojciech Skomorowski)
- Fix orbitals not being printed to .fchk file used by IQmol (Kuan-Yu Liu)
- Enable FAST_XAS crash with STATE_ANALYSIS = TRUE or GUI = 2 (Kaushik Nanda)
- Fix incompatibility of SCF_FINAL_PRINT and DC-DFT (John Herbert)
- Fix failure to conserve molecular point-group symmetry in libopt3 (Andrew Gilbert)
- Fix file error when calculating TS-VDW forces (John Herbert)

Density functional theory and self-consistent field:

New ``Robust SCF'' procedure provides more reliable SCF convergence via automated choice of algorithm and defaults (Kaushik Nanda)
Performance enhancements for medium to large DFT energy and force calculations via new Coulomb algorithm based JK and RI-JK derivatives (Xintian Feng)
Canonical ROHF/ROSCF (Adrian L. Dempwolff)
Charge-transfer metrics for TDDFT (John Herbert)
TDDFT-1D provides improved TDDFT/TDA where the crossing of S1/S0 states is smooth (Vishikh Athavale, Hung-Hsuan Teh, Joseph Subotnik)
Resolved issues with:
- Crash of ALMO-CIS/TDA with large basis sets (Yuezhi Mao)
- DFT numerical quadrature consistency check not always performed (Xintian Feng)

Correlated methods:

EOM-CCSDT for EE, SF, IP, EA, DIP and DEA (Manisha, Prashant Uday Manohar)
Added parallel performance to EOM-CCSDT (Manisha)
Analytic gradients for EOM-DEA/DIP-CCSD methods (Tingting Zhao, Anna Krylov)
Spin-orbit coupling calculations for EOM-DEA/DIP-CCSD methods (Tingting Zhao, Sai Kotaru, Sahil Gulania, Pavel Pokhilko, Anna Krylov)
Automated calculations of Coulomb wave for caluclations of Auger rates within the Feshbach--Fano framework (Saikat Roi, Wojciech Skomorowski)
Auger Channel Projection EOMIP-CCSD with frozen core and open shell references (Robin Moorby, Florian Matz, Thomas Jagau)
Complex-valued RI-EOM-CCSD (Simen Camps, Cansu Utku, Thomas Jagau)
EOM-(EE/SF)-CCSD dynamic polarizability for imaginary frequencies (Kaushik Nanda)
Improved EOM-CC anisotropic polarizability formula (Kaushik Nanda)
CC2 with size-consistent Brillouin--Wigner Partitioning (Linus Dittmer, Nikolay V. Tkachenko, Martin Head-Gordon)
Maximum Physical Regularization for size-consistent Brillouin-Wigner Theory (Linus Dittmer, Nikolay V. Tkachenko, Martin Head-Gordon)
BW-S2 performance improvements (Zhenling Wang, Martin Head-Gordon)
Extend 1eX2C to calculate spin-orbit coupling components (Richard Kang, Martin Head-Gordon)
New algorithm to accelerate 1C-NOCIS calculations using generalized non-orthogonal Slater-Condon rules (Rachel Lynn Patterson, Martin Head-Gordon)
Implementation of coupling between Dyson orbitals and the continuum (plane wave) (Madhubani Mukherjee, Anna I. Krylov)
Add a switch to control averaging in DO/PW coupling calculation (Madhubani Mukherjee, Anna I. Krylov)
Resolved issues with:
- Coupled cluster PES scans erroneously reporting SCF energy (Kaushik Nanda)
- Convergence difficulties in DIP-EOM-CCSDT (Manisha)
- Crash due to memory allocation issues in Auger decay width calculations for certain basis sets (Saikat Roy, Wojciech Skomorowski)

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

SAPT+PCM, dielectric boundaries for (X)SAPT calculations (John Herbert)
Heterogeneous PCM allows users to modify the dielectric for each atom in PCM (John Herbert)
Seminumerical frequency support for the SMD solvation model (John Herbert)
Energy-based generalized many-body expansion (GMBE) implementation (Jake A. Tan, Francisco Ballesteros, Ka Un Lao)
Density matrix-based generalized many-body expansion (GMBE) implementation (Jake A. Tan, Francisco Ballesteros, Ka Un Lao)
Allow user-defined vdW radii for Poisson equation solver, PEqS (John Herbert)
Enable user to explicitly set polarization screening factor in EFP (Kaushik Nanda)
Resolved issues with:
- Many-body calculations with gradients fail with FILE_MO_COEFS error (Kaushik Nanda, Ryan Steele)
- Missing EFP polarization energy at every SCF step when USE_LIBQINTS = TRUE (Xintian Feng)
- Disabled NAC calculations with SMD (John Herbert)
- Printing spatial overlaps of occ-virt orbital pairs, SPATIAL_OVERLAP_ANALYSIS (John Herbert)

Tools for studying chemistry in standard and unusual regimes:

New mechanochemical pressure model using PV term energy correction (Felix Zeller)
Added torsional and flat-bottom potential restraints for geometry optimizations (Chance W. Lander, Yihan Shao)
Added bond stretch, r12pr34, angle, 1 to midpoint of 2 atoms, 1 to COM, and dihedral restraints to list of available restrained PES scan options (Chance W. Lander, Yihan Shao)

Fragment and energy decomposition analysis:

Broken bond orbitals (BBOs) (Alistair J. Sterling, Daniel S. Levine, Abdul Aldossary, Martin Head-Gordon)
Enable ALMO(MSDFT) diabatic coupling calculation involving Delta-SCF excited states (Yuezhi Mao)
Uncoupled FERF (Hengyuan Shen, Abdul Aldossary, Martin Head-Gordon)

Incorporation of quantum nuclear effects (NEO suite):

NEO-PCM analytic Hessian for solution phase frequency and normal mode analysis (Mathew Chow, Sharon Hammes-Schiffer)
External point charges are now supported for NEO electrostatic embedding calculations (Mathew Chow, Sharon Hammes-Schiffer)
Enabled exchange-correlation functionals that have additional dispersion correction baked-in (e.g., wB97X-D, wB97X-D3, B3LYP-D3(BJ), etc.) to be used in NEO-DFT (Mathew Chow, Sharon Hammes-Schiffer)
Added full DFT-D support for NEO (energies, gradients, Hessians) and RT-NEO (real-time and real-time-Ehrenfest) calculations (Mathew Chow, Sharon Hammes-Schiffer)
Pseudopotentials are now fully supported with NEO (including energies, gradients, and Hessians) (Mathew Chow, Sharon Hammes-Schiffer)
DIIS_GDM is now supported for the NEO simultaneous solver (Mathew Chow, Sharon Hammes-Schiffer)
Improved performance by:
- Simultaneous GDM optimization for NEO-HF and NEO-DFT methods (Mathew Chow, Sharon Hammes-Schiffer)
- Nuclear SCF initial guess (Mathew Chow, Sharon Hammes-Schiffer)
- Generalized simultaneous DIIS and GDM optimization to treat 'N' number of quantum protons to achieve faster NEO Hartree Product calculations (Mathew Chow, Sharon Hammes-Schiffer)
- Various improvements to simultaneous NEO-PCM calculations, including support with Hartree product and multiple proton CNEO Hessian calculations (Mathew Chow, Sharon Hammes-Schiffer)
- Updates and improvements to general orbital optimizer library (Christopher Malbon, Sharon Hammes-Schiffer)
- Performance improvements to CNEO Hessian calculations via addition of preconditioner (Eno Paenurk, Sharon Hammes-Schiffer)
- Improved stability and performance for NEO Hessian and CNEO Hessian codes (Mathew Chow, Sharon Hammes-Schiffer)
Resolved issues with:
- Fixed issue where nuclear AUTOSAD would not read NEO_PURECART for child instructions (Mathew Chow, Sharon Hammes-Schiffer)
- Fixed issue where MAX_SCF_CYCLES did not have an effect on the simultaneous NEO-SCF solvers (Mathew Chow, Sharon Hammes-Schiffer)
- Fixed memory issue for calculations using NEO simultaneous SCF combined with NEO Hartree product (Mathew Chow, Sharon Hammes-Schiffer)

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