In your original settings I didn't see any ARMCI_NETWORK setting at all (when building with the build_nwchem script that is fine but otherwise it isn't). In any case you seem to have MPI so you could try ARMCI_NETWORK=MPI-TS. I have no way of testing whether that will actually work in your setup, but it asks ARMCI to build using MPI as the communication fabric. I would be surprised if that wouldn't work.