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Gaussian

Gaussian provides state-of-the-art capabilities for electronic structure modeling and is licensed for a wide variety of computer systems.Gaussian is an electronic structure program, used by chemists, chemical engineers, biochemists, physicists and other scientists worldwide, and provides a wide-ranging suite of the most advanced modeling capabilities available. You can use it to investigate the real-world chemical problems that interest you, in all of their complexity, even on modest computer hardware.

Starting from the fundamental laws of quantum mechanics, Gaussian predicts the energies, molecular structures, vibrational frequencies and molecular properties of compounds and reactions in a wide variety of chemical environments. Gaussian's models can be applied to both stable species and compounds which are difficult or impossible to observe experimentally, whether due to their nature (e.g., toxicity, combustibility, radioactivity) or their inherent fleeting nature (e.g., short-lived intermediates and transition structures).

With Gaussian, you can thoroughly investigate the chemical problems that interest you. For example, not only can you minimize molecular structures rapidly and reliably, you can also predict the structures of transition states, and verify that the predicted stationary points are in fact minima or transition structure (as appropriate). You can go on to compute the reaction path by following the intrinsic reaction coordinate (IRC) and determine which reactants and products are connected by a given transition structure. Once you have a complete picture of the potential energy surface, reaction energies and barriers can be accurately predicted. You can also predict a wide variety of chemical properties.

What Sets Gaussian Apart from Other Programs?

  • Gaussian produces accurate, reliable and complete models without cutting corners.
  • A wide variety of methods makes Gaussian applicable to a broad range of chemical conditions, problem sizes and compounds.
  • Gaussian provides state-of-the-art performance in single CPU, multiprocessor/multicore and cluster/network computing environments.
  • Setting up calculations is simple and straightforward, and even complex techniques are fully automated. The flexible, easy-to-use options give you complete control over calculation details when needed.
  • Results from all calculation types are presented in natural and intuitive graphical form by GaussView.

Comprehensive Investigations

Comprehensive Investigations of Molecules and Reactions

With Gaussian, you can thoroughly investigate the chemical problems that interest you. For example, not only can you minimize molecular structures rapidly and reliably, you can also predict the structures of transition states, and verify that the located stationary points are in fact minima and transition states. You can go on to compute the reaction path by following the intrinsic reaction coordinate (IRC) and determine which reactants and products are connected by a given transition structure. Once you have a complete picture of the potential energy surface, reaction energies and barriers can be accurately predicted.

Researchers have used these fundamental capabilities of Gaussian to study isopenicillin N synthase (IPNS), a member of a family of mononuclear nonheme iron enzymes (illustrated at the bottom right of the next image). Transition metal enzymes catalyze some of the most important biochemical processes, and they can also serve as inspiration for novel biomimetic catalysis. In the latter context, these researchers wanted to determine how the metal center and the protein matrix separately contribute to the enzyme system's catalytic activity. They analyzed the catalytic mechanism of IPNS, exploring the potential energy surface for the transformation of the tripeptide substrate d-(l-a-aminoadipoyl)-l-cysteinyl-d-valine (ACV) to isopenicillin N (IPN). The ONIOM facility in Gaussian enables the transition structures and reaction paths to be computed for the reactions involving large proteins like this system.


Reference: M. Lundberg, T. Kawatsu, T. Vreven, M.J. Frisch & K. Morokuma, JCTC 5 (2009) 222.

The reactants (left), transition structure (center) and products (right), as well as the IRC reaction path, are all computed using the ONIOM facility. The highlighted inset focuses on the active atoms in the high accuracy layer, treated with density functional theory. The grey region outside is a tiny portion of the low accuracy layer, treated with molecular mechanics in the integrated QM:MM method.

A small part of their results are shown in the illustration above depicting the reactants, products and transition structure for a proton transfer reaction. Overall, their analysis suggests that the main catalytic effect comes from the metal center while the protein environment controls the high product specificity.

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