PQS AB INITIO MODULE CAPABILITIES

• 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).

SCALED QUANTUM MECHANICAL (SQM) FORCE FIELD MODULE

For fitting 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



Friday, 23-May-08 09:41:04 PDT