Capabilities
PQS ab initio v. 4.0
Our flagship, primarily ab initio software suite offers highly efficient, fully parallel implementations of all the major calculational methods along with some features unique to PQS. New in version 4.0 are efficient parallel implementations of high-level correlated energies for MP3, MP4, CID, CISD, CEPA-0, CEPA-2, QCISD, QCISD(T), CCD, CCSD and CCSD(T) wavefunctions; enforced geometry optimization (used, among other things, to simulate the results of Atomic Force Microscopy (AFM) experiments); full-accuracy, canonical UMP2 energies and analytical polarizabilities and hyperpolarizabilities for HF and DFT wavefunctions.
Current capabilities include:
- An efficient vectorized Gaussian integral package allowing high angular momentum basis functions and general contractions.
- Abelian point group symmetry throughout; utilizes full point group symmetry (up to Ih) for geometry optimization step and Hessian (2nd derivative) CPHF.
- Closed-shell (RHF) and open-shell (UHF) SCF energies and gradients, including several initial wavefunction guess options. Improved SCF convergence for open-shell systems.
- Closed-shell (RHF) and open-shell (UHF) density functional energies and gradients including all popular exchange-correlation functionals: VWN, B88, OPTX, LYP, P86, PW91, PBE, B97, HCTH, B3LYP, make up your own functional etc.
- Fast and accurate pure DFT energies and gradients for large basis sets using the Fourier Transform Coulomb (FTC) method.
- Efficient, flexible geometry optimization for all these methods including Baker's Eigenvector Following (EF) algorithm for minimization and saddle-point search, Pulay’s GDIIS algorithm for minimization, use of Cartesian, Z-matrix and delocalized internal coordinates. Includes new coordinates for efficient optimization of molecular clusters and adsorption/reaction on model surfaces.
- Full range of geometrical constraints including fixed distances, planar bends, torsions and out-of-plane bends between any atoms in the molecule and frozen (fixed) atoms. Atoms involved in constraints do not need to be formally bonded and - unlike with a Z matrix - desired constraints do not need to be satisfied in the starting geometry.
- Analytical (and numerical) second derivatives for all these methods, including the calculation of vibrational frequencies, IR intensities, VCD rotational strengths and thermodynamic analysis.
- Efficient NMR Chemical Shifts for closed-shell HF and DFT wavefunctions.
- A full range of effective core potentials (ECPs), both relativistic and non-relativistic, with energies, gradients, analytical second derivatives and NMR.
- Closed-shell MP2 energies and analytical gradients and dual-basis MP2 energies; numerical MP2 second derivatives.
- Potential scan, including scan + optimization of all other degrees of freedom.
- Reaction Path (IRC) following using either Z-matrix, Cartesian or mass-weighted Cartesian coordinates.
- Conductor-like screening solvation model (COSMO) including energies, analytical gradients, numerical second derivatives and NMR.
- Population analysis, including bond orders and atomic valencies (with free valencies for open-shell systems); CHELP and Cioslowski charges.
- Weinhold's Natural Bond Order (NBO) analysis, including natural population and steric analysis.
- Properties module with charge, spin-density and electric field gradient at the nucleus.
- Polarizabilities and dipole and polarizability derivatives; Raman intensities.
- Full Semiempirical package, both open (unrestricted) and closed-shell energies and gradients, including MINDO/3, MNDO, AM1 and PM3. For the latter, all main group elements through the fourth row (except the noble gases) as well as Zinc and Cadmium, have been parametrized.
- Molecular Mechanics using the Sybyl 5.2 and UFF Force Fields.
- QM/MM using the ONIOM method.
- Molecular dynamics using the simple Verlet algorithm.
- Pople-style input for quick input generation and compatibility with other programs.
- Graphical input generation and display
- All major ab initio functionality is fully parallel (except MP2 gradients which is serial only - parallel version under development).
PQSMol v. 1.2
Graphical User Interface to the PQS ab initio program
containins
a model builder (with two mechanics force fields), job input preparation,
serial and parallel job submission (including an interface to SGE,
DQS and PBS job queues as well as PVM control) and post-job visualization
and display. The latter includes molecular orbitals (cononical,
localized
and natural), electron densities, electrostatic potentials, optimization
history, dynamics trajectories, animation of normal modes and simulation
of IR/Raman, NMR and VCD spectra. See a
screenshot of PQSMol in
action or download a trial verson for
Linux or
Windows
(Linux rpm, tarball, 32-bit and 64-bit versions available on the software page).
SQM v. 2.0
The Scaled Quantum Mechanical (SQM) Force Field Module is used
for fitting of the calculated results to experimental vibrational spectra. Scale
factors can be optimized for best fits to a given set of experimental
fundamentals. Precalculated scale factors (for H, C, N, O and Cl) give
better agreement with experiment for both vibrational frequencies and IR
intensities.
