Semichem, Inc. — Providers of Solutions for Computational Chemistry

Semiempirical Quantum Mechanics

Transition States and Intermediates

Advanced CHN and FULLCHN methods for locating intermediates and transition states along a single- or multi-step reaction path specified by two or more input geometries.

Multiple Minima Searches

Fully-customizable simulated annealing to automatically find multiple minima (conformers, structural isomers) or other critical points (i.e. transition states).

Robust Optimization Methods

Efficient and robust geometry optimizations (constrained or unconstrained) in Z-matrix or Cartesian coordinates. Both gradient-based or Hessian-based energy minimization methods (TRUSTE and NEWTON) are available for energy minima. Energy/gradient minimization methods (TRUSTG and LTRD) are available for local transition states.

Fast Stationary Point Characterizations

Innovative LFORCE and HESSEI methods for fast, accurate characterization of stationary points without the need for full frequency calculations.

PES Scans

Relaxed scanning of potential energy surfaces using one or two geometric coordinates

Intrinsic Reaction Paths

Integration of intrinsic reaction paths from transition states to products and reactants using IRC or PATH methods.

Properties

Heats of formation, other thermodynamic properties, vibrational spectra, dipole moments, polarizabilities and hyperpolarizabilities, electronic spectra, ESR, charge distributions, bond orders, and unpaired spin denisties.

Partial Atomic Charges

Excited States

Calculate excited state geometries and corresponding properties and compute vertical transition energies, transition dipole moments and oscillator strengths from the ground state to any number of excited states using our advanced configuration interaction (CI) methods.

QSAR Output

Simple generation of all output used by the CODESSA QSAR package, via the "CODESSA" keyword.

Batch Execution

Submit multiple AMPAC input files and request AMPAC 8 to automatically run then in sequence.

Semiempirical Models

Calculation Types

Energies, optimizations, frequencies, relaxed PES scans, transition state and intermediate searches, annealing, IRCs.

Solvation

Treatment of solvated systems using COSMO or our optional AMM-2001 (AMSOL Model Module is available for an additional charge. Please contact Customer Service for details.)

Configuration Interaction (C.I.)

Fast and robust, handling singlets (S), singlets-doublets (SD), singlest-doublets-triplets (SDT) or complete active space (CAS) within any set of MOs. AMPAC's CI can be used for all calculation types with open shell systems and/or excited states. Also, AMPAC's C.I. implantation is fully analytical (not numerical) for much better results and vastly increased speed.

Excited States

Calculate excited state geometries and corresponding properties and compute vertical transition energies, transition dipole moments and oscillator strengths from the ground state to any number of excited states using our advanced configuration interaction (CI) methods.

Speed

Reliability

More robust than any competing product for all calculations, including SCF convergence, geometry optimizations, transition state location, frequencies, solvation and C.I.

Memory Efficiency

Dynamic memory allocation, so AMPAC 8 uses far less memory than previous versions and itself imposes no limits on job sizes (number of atoms, size of C.I. active space, etc.).

Documentation

Comprehensive manual providing descriptions of all input, examples, discussion of all methods and literature references. Complete list of changes from version to version.
Active Maintenance and Development
AMPAC (along with AGUI) is constantly being improved (also see here for changes made since AMPAC 8 was first released) in response to customer feedback, market demands, new ideas and methods in the literature, changes in the computing landscape as well as the interests of our own researchers and collaborators.