What Axel says is correct. Moreover, the details of how the structure is
initially constructed
are deliberately isolated from the elastic constant calculation by putting
it a separate include file, init.mod, the first line of which
says:
"# NOTE: This script can be modified for different atomic structures,
# units, etc. See in.elastic for more info."
So, feel free to get creative with this. Also, try taking Axel's advice
about trying to figure
things out for yourself.
Aidan