Described below are two methods for preparing input files with basis sets and ECPs which are not currently built in. Both are useful for geometry optimization restarts since the coordinates occur together in a block, and not mixed up with basis set information.

1. Using the preprocessing function with external basis set and ECP files

Download the required basis sets and ECPs from the EMSL site https://bse.pnl.gov/bse/portal

Make text files with the basis set and/or ECP for each element. Basis set files need to be terminated with a blank line, ECP files should not have a final blank line.

Put basis sets and ECPs in directories (called here def2_svp_BAS and def2_ecp_ECP but you can call them whatever you want) and copy them to the Firefly directory.

Prepare your input file as for the little metal complex in prep_example.inp and then run it: firefly -i prep_example.inp -o prep_example.out

This checks the input is going to be OK, and generates a file called 'input' which is here renamed example.inp.

All the information is now present in example.inp so can be run without needing external files e.g. on remote systems if you don't want to keep transferring or updating basis set/ECP directories.

Or if your basis set/ECP directories are already present you can just comment out the check run in prep_example.inp and run it directly.

2. Using an external basis set file in $BASIS (extfil=.t.)

Instead of separate files for each element the basis set can be defined as single file called basis.lib by default. Firefly needs access to this file to run the job (its usually in the same directory, see elsewhere on the forum for more information on this feature). The file prep_extfil_example.inp shows how this works - putting GBASIS=SVP instructs the program to use only SVP basis sets within basis.lib.

Unfortunately ECP information can’t be incorporated in this way, and either has to be pasted in manually or by using the preprocessing feature. Running prep_extfil_example.inp and renaming the file called 'input' simply produces the file extfil_example.inp, now containing the full ECP group.

As above, if your basis set/ECP directories are already present you can just comment out the check run in prep_extfil_example.inp or extfil_example.inp and run them directly.

Both methods can also be used for preparing gamess (us) files - the check runs may not terminate properly due to certain keywords, but a useable file called 'input' is normally generated.

Here you can find archive with samples.