The locations of folders that contain MOPAC reference data sets is given by REF=text[;text[;text[;text]]] . For example:
ref= &
"../../reference data/Data Intermolecular
interactions/S22 Intermolecular"; &
"../../reference data/Data Intermolecular
interactions/S22 Separated"; &
"../../reference data/Data Intermolecular
interactions/Water dimers all"; &
"../../reference data/Data Intermolecular
interactions/D3H4 Ionic Intermolecular"; &
"../../reference data/Data
Intermolecular interactions/D3H4 Ionic Separated"; &
"M:/PARAM/reference
data/Data normal"; &
../../reference data/Data_levels
Using ampersands, "&", makes reading the REF keyword easier. Filenames and path must be in quotation marks if they contain spaces, if there are no spaces, quotation marks are optional.
As these names tend to be long, a convenient way of shortening them is to share the folders, then map the network drive. So on a Windows machine, if the reference data folders were shared and mounted as:
N:\ = C\Users\myname\PARAM\reference data\data normal
E:\ = C\Users\myname\PARAM\reference
data\data exotic
L:\ = C\Users\myname\PARAM\reference data\data
states
then the keyword could be shortened to ref=N:\;E:\;L:\
The procedure when PARAM is run on a Mac and Linux is similar. The reference data folders are shared on the Windows platform, then mounted on the Mac platform. An alternative is to have a mirror copy of the reference data folders on the Mac or Linux machine, and update these folders using a command of the type:
rsync -v -u -r '/Volumes/Software on Windows machine/PARAM/Reference data/ '/Users/MyName/PARAM/Reference data'
The order of searching is first folder, then second, then third, etc.