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Review of Gaussian 94W


Jim Beatty
Chemistry Department, Ripon College
Ripon, WI 54971

Note: This article was scanned using OCR from the Spring 1996 CCCE Newsletter. Please contact us if you identify any OCR errors.
          Gaussian has long been the premier ab initio quantum chemistry program. Recently, an other ab initio program, Mulliken, has appeared. However, Gaussian is the only one that will run on a PC platform. The full implementation is available in the Windows 3.1 environment. Gaussian has powerful molecular modeling features and will calculate optimum geometry and energy, vibrational frequencies, excited states, thermochemical properties, and a wide range of other molecular properties. Transition states and solvent effects may be investigated. Gaussian is not a display program. The user may directly communicate with molecular modeling programs such as PC Model and HyperChem for visualization of structures.
          We have been using Gaussian 94W for the past eight months for a senior student research project, and lately in the quantum chemistry part of our physical chemistry course on a Pentium 75 MHZ computer. Previously, we used Gaussian 92 on a 486 computer. The combination of the jump to Gaussian 94W, the Pentium based computer, and our experience has made Gaussian 94W an interesting and useful addition to our program. We also have the CAChe molecular modeling program running on a Power Mac to complement the ab initio calculations of Gaussian 94W.
          The minimum requirements to run Gaussian 94W is an lntei80486/0X or higher, 16MB or more of memory, 80 MB of disk storage, 100 MB of scratch disk space, and Windows 3.1 or higher. The price is $750 for a single machine copy for educational use. The program comes with a user reference guide and a text, Exploring Chemistry with Electronic Structure Methods. The text contains chapters with sample calculations to run. The sample files in the chapters are included in the tutor subdirectory in the program. All that you need is time on the computer to run the sample calculations to learn how to use Gaussian 94. Recently I upgraded my machine from 16 MB to 24 MB of memory. This increased the speed of calculations significantly by decreasing the need to swap files. The only problem we have had is the linking of calculations and this may be due to not trying hard enough. We have transferred the small amount of needed data manually. I am using Windows 3.1 and plan to install Windows 95 to see how the performance changes. The interface is easy to use. An understanding of Fortran is helpful in setting up and understanding the data files. The interface to run caculations is user friendly.
          Gaussian 94W is an appropriate addition to the physical chemistry laboratory program. A recent flyer on the forthcoming 6th edition of Shoemaker, Garland, and Nibler's Experiments in Physical Chemistry indicates that they are including experiments using Gaussian 94W. We have calculated bond energies, thermodynamic properties, vibrational frequencies, potential curves, and equilibrium structures. Our calculations have been for two to four atom molecules. Most calculations have been the order of minutes with potential energy surfaces running to hours. Basis sets have been investigated. The results are compared with literature values and infrared spectroscopy experiments. Students are impressed by the accuracy of the calculations which run from a few to about ten percent. The calculations fit well into a four hour laboratory with the same molecule being investigated on the CAChe semi empirical program on a Power Mac. The potential energy calculation is run over night.
          The senior research student is using Gaussian 94W and CAChe for his senior research thesis project. CAChe is used for preliminary work, displaying structures, and for complementary semi empirical calculations. Gaussian based calculations are the major part of the effort. After performing the tutor calculations in Exploring Chemistry with Electronic Structure Methods he has expanded to molecules of his own selection. He has explored the capabilities of Gaussian on the PC platform and has given himself a senior-first year graduate course in quantum chemistry. I have been impressed by his progress and accomplishments. Again, calculations have been restricted to small molecules to keep computation times down.
          In conclusion, Gaussian 94W is worth the cost. Students will have an understanding of the ultimate in quantum computational chemistry. They should view programs such as Gaussian as another experimental instrument available to all chemists. If you need more information on Gaussian, order a copy of Exploring Chemistry with Electronic Structure Methods. This text should be in every undergraduate library.
Gaussian, Inc.
Carnegie Office Park, Bldg. 6
Pittsburgh, PA 15106
Voice: 412 279·6700
Fax: 412·279·2188


03/21/96 to 03/25/96