Q-Chem 3.0 is a comprehensive ab initio quantum chemistry package

New Features in Q-Chem 3.2
(click here for supported platforms)

  • Several new DFT functional options:
    • Long-ranged-corrected (LRC) functionals
    • Baer-Neuhauser-Livshits (BNL) functional
    • Variations of ωB97 Functional
    • Constrained DFT (CDFT)
    • Grimme’s empirical dispersion correction
  • Solvation models:
    • SM8 model (energy and analytical gradient) for water and organic solvents
    • Updates to Onsager reaction-field model
  • Intermolecular interaction analysis:
    • SCF with absolutely localized molecular orbitals for molecule interaction (SCF-MI)
    • Roothaan-step (RS) correction following SCF-MI
    • Energy decomposition analysis (EDA)
    • Complementary occupied-virtual pair (COVP) analysis for charge transfer
    • Automated basis-set superposition error (BSSE) calculation
  • Electron transfer analysis
  • Relaxed constraint algorithm (RCA) for converging SCF
  • G3Large basis set for transition metals
  • New MP2 options:
    • Dual-basis RIMP2 energy and analytical gradient
    • O2 energy and gradient
  • New wavefunction-based methods for efficiently calculating excited state properties:
    • SOS-CIS(D) energy for excited states
    • SOS-CIS(D0) energy and gradient for excited states
  • Coupled-cluster methods:
    • IP-CISD energy and gradient
    • EOM-IP-CCSD energy and gradient
    • OpenMP for parallel coupled-cluster calculations
  • QM/MM methods:
    • QM/MM full hessian evaluation
    • QM/MM mobile-block hessian (MBH) evaluation
    • Description for MM atoms with Gaussian-delocalized charge
  • Partial Hessian method for vibrational analysis
  • Wavefunction analysis tools:
    • Improved algorithms for computing localized orbitals
    • Distributed multipole analysis
    • Analytical Wigner intracule


New Features in Q-Chem 3.1

  • Several new DFT functional options:
  • Faster correlated excited state method: RI-CIS(D)
  • Potential energy surface crossing minimization with EOM-CCSD
  • Dyson orbitals for ionization from the ground and excited states within CCSD and EOM-CCSD methods


New Features of Q-Chem 3.0

Q-Chem 3.0, a new major release, is a comprehensive ab initio
quantum chemistry package -- the ultimate quantum solution to problems of all sizes. It is available fully-integrated as the back end of Spartan '06 and stand-alone (LINUX, Mac OS and other UNIX platforms).

Q-Chem 3.0: Making a Difference

Key Features Innovation Benefit
NMR Chemical Shifts 1st Linear-scaling NMR Feasible for hundreds of atoms
Fast DFT Calculations New FTC and DFT methods Up to 3 times faster
Fast MP2 Calculations RI-MP2 (with gradients) RI-TRIM local MP2 3 to 10 times faster
Scaled MP2 Schemes New SOS-MP2, MOS-MP2 schemes with RI, gradients More accurate and faster
Coupled Cluster Methods EOM-(EE, IP, EA, SF)-CCSD methods with gradients and properties Robust and efficient treatment of open-shell and electronically excited species
Valence Correlation Models SSG, PP, IP, RP methods with gradients Inexpensive alternative to GVB/CASSCF-type models
QM/MM Hybrid Methods ONIOM Energy, Gradient, Frequency Suitable for huge structures
Anharmonic Frequencies New TOSH Model Direct prediction of IR peaks
Continuum Solvation Model SS(V)PE Electronic Model Improved accuracy for ions
Parallel DFT/HF Energies, gradients and frequencies (with distributed memory) Scalable to many CPUs
Dual Basis Methods HF, DFT, MP2 energies About 10 times faster for
large basis sets
Transition Structure Finder Growing String Method Improved search Tool
Direct Dynamics Extended Lagrangian and
Born-Oppenheimer
Enables trajectory studies
Graphic User Interface WebMO on distribution CD Basic builder and viewer

For a complete list of features please see Q-Chem User's Guide


Q-Chem in Action

> Fast DFT on Linux Clusters

It takes Q-Chem 8 minutes to do an energy and gradient calculation for this 103-atom taxol molecule at BLYP/6-311G (df,pd) level with 2000 basis functions on an 8-cpu opteron cluster.

> MP2 at HF Speed

Highly efficient resolution-of-the-identity (RI) algorithms make medium & large basis MP2 calculations much more efficient, as shown in this example of computing the relative conformational energy of alanine
tetrapeptide (there are 27 low-lying structures!).

> Linear-Scaling NMR Calculation

This diagram and table show the convergence of NMR shifts of the depicted object (N-methyl nicotinamide surrounded by hundreds of water molecules) versus the number of surrounding water molecules. They represent the largest NMR calculations, with up to 9000 basis functions at HF/6-31G** level.

> A New Finding

Q-Chem’s unique EOM-SF-CCSD method, which is capable of efficiently describing multiple states of di- and tri-radicals, was used to discover the first example of an organic molecule with an open-shell doublet ground state. These three unpaired electrons are coupled antiferromagnetically in the DMX triradical.

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