Generating Input Files for Gaussian

We recognize that some Jaguar users also use Gaussian for calculations. Therefore, Jaguar can generate or read Gaussian input files.

You can use the GUI as a convenient tool to create Gaussian input files. The output file that is produced from the Jaguar run and whose name ends in .gau can be used as a Gaussian input file. The .gau file requests an HF or ROHF (restricted open-shell Hartree-Fock) calculation, whichever is appropriate for the number of electrons in the system, unless you choose to specify another method.

To create a .gau file, select the Gaussian input file (.gau) option in the Output tab. If you are just creating a Gaussian input file and you do not want to use Jaguar to generate a converged wave function, you can save some time by choosing Initial Guess Only from the Jaguar submenu of the Applications menu, or using the Edit Job dialog box to add the keyword setting igonly=1 (initial guess only) to the gen section of the input file.

The information in the .gau file depends on the information you have provided. The file always contains a molecular geometry (in Cartesian coordinates and angstroms); instructions for how to input geometries are available in Setting Up a Jaguar Input File. The file also specifies the molecular charge and the spin multiplicity of the molecule. If you want either of these values to be non-zero, you can make the appropriate settings in the Molecule tab. You can also set the name of the basis set you want to provide in the .gau file (for example, STO‑3G) using the Molecule tab. (The default basis set choice is 6‑31G**.)

To actually generate the .gau file, you need to run the Jaguar job you have just specified. See Running Jaguar Jobs for information on running jobs.

Other Jaguar Options for the .gau File

You can use a Jaguar input file to run a Jaguar job which generates a .gau file. See The Jaguar Input File for a description of input files. Selecting the Gaussian input file (.gau) output option described above corresponds to setting the output keyword ip160 to 2 in the gen section of the input file.

You can create or edit Jaguar input files by hand, making keyword settings corresponding to all of the relevant options described above; see The Jaguar Input File for details. If you want, you can make some of the desired settings in the GUI, use the Jaguar Write dialog box to save a Jaguar input file, and edit it by hand later to set other keywords.

You can generate additional information for the .gau file by setting the output keyword ip160 in the gen section of the input file to 3, 4, or 5. Setting this keyword to 3 lets you provide an initial guess within the .gau file. Setting it to 5 allows you to explicitly provide the basis set itself, rather than just the basis set name, within the .gau file. This option is useful for specifying basis sets which are included in Jaguar but not in Gaussian. Setting ip160 to 4 allows you to include both the initial guess and the basis set in the .gau file.

Writing Orbitals for Gaussian

You can write orbitals from Jaguar in the format used by Gaussian (for its “guess=cards” option) by choosing to print the appropriate orbitals from the Output tab, which is described in Jaguar Output Options for Orbitals. You must choose the f19.15 or f8.5 format from the Format option menu.