(AFM) experiments); full-accuracy, canonical UMP2 energies and analytical polarizabilities and hyperpolarizabilities for HF and DFT wavefunctions. 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. Productive, adaptable geometry optimization for every one of these methods including 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. Expository second subsidiaries for every one of these systems, including the calculation of vibrational frequencies, IR intensities 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