Exciting 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 3000 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.