Before Getting Started: A Warning about Scratch Files

Generally, electronic structure programs like PSI3 make significant use of disk drives. Therefore, it is very important to ensure that PSI3 is writing its temporary files to a disk drive phsyically attached to the computer running the computation. If it is not, it will significantly slow down the program and the network. By default, PSI3 will write temporary files to /tmp, but you will want to set up a default scratch path (as described in sections 3.5 and 3.6) because the /tmp directory is usually not large enough except for small test cases. In any event, you want to be very careful that you are not writing scratch files to an NFS-mounted directory that is physically attached to a fileserver elsewhere on the network.