Mod:gauss
Instructions for Use of the Gaussview System
The Gaussview software can be run on the Windows or MacOS X Computers.
- Start Gaussview from the Start/Programs menu (Windows) or the OS X Dock (Apple). If you use a Mac, and the latter does not succeed, try instead to open a terminal window and from this, type gv. [There seems to be a subtle problem with the internal Unix environment which causes this, it will hopefully be fixed soon].Gaussview is generally used to initialise Gaussian Molecular Orbital calculations using pre-built structures derived from either Chem3D or CAChe and which have been already saved in MDL Molfile format (with a .mol filename extension). Ignore the Fragment window that appears when you start the program and the empty molecule window, and proceed to File/open to import a pre-built structure. You can if you wish use the GaussView editor to construct a molecule from scratch (use the built in help pages for details). Use Edit/Clean to produce a meaningful 3D initial structure; this is not quite as reliable as a proper Molecular Mechanics calculation, but for many cases it may be adequate.
- Start a Gaussian calculation by selecting the following settings:
Job Type: Optimization (optionally select Optimization+frequencies if you dont mind waiting a bit longer); Method: Ground State, Hartree-Fock, 6-31G Basis set; Link 0: %chk=yourfilename.chk, %mem=256MB; Guess: Save orbitals to checkpoint file. The checkpoint entry is particulary important, since you will use this file to generate MO diagrams etc. [You can try other options of course if you wish]. Press submit. - Following file dialogs to save the resulting input file, the calculation will take a few minutes to complete.
- Open the Checkpoint file you specified above (yourfilename.chk). Be careful not to click the mouse in this window, since this action will add the current fragment (normally methane) to this molecule window. If you want to move the window around on the screen, click only on the top bar for the window.
- Results/Summary does what it says on the tin! Record the total energy in your report.
- Results/surfaces opens up a dialog to specify cube actions and generate a new cube. A program called Cubgen will run for a few minutes. </
- When generation is complete, specify a surface:
- View/display format allows you to set the surface to transparent. Edit/MOs will allow you to inspect/record the energy of any molecular orbitals generated as surfaces (the energies are in Hartree).
- File/Save image allows an image file of the surface to be saved, for eventual use in your report.
