NWChem is a computational chemistry code based on gaussian basis functions or plane-waves.
The default command to start NWChem is nwchem PREFIX.nw > PREFIX.out. You can change that by setting the environment variable ASE_NWCHEM_COMMAND.
Here is an example of how to calculate optimize the geometry of a water molecule using PBE:
$ asec H2O optimize -c nwchem -p xc=PBE
LBFGS: 0 16:17:29 -2064.914841 1.9673
LBFGS: 1 16:17:31 -2064.963074 0.9482
LBFGS: 2 16:17:32 -2064.976603 0.1425
LBFGS: 3 16:17:33 -2064.977216 0.0823
LBFGS: 4 16:17:35 -2064.977460 0.0010
$ ase-gui H2O.traj@-1 -tg "a(1,0,2),d(0,1)"
102.577881445 1.00806894632