Instructions to build with OpenMPI are outdated
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Forum Vet
10:59:33 AM PST - Mon, Jan 21st 2019
Those instructions are indeed obsolete.
Since NWChem 6.6 we do not recommend setting any MPI env. variable, but to simply point PATH to the mpif90 in use
https://github.com/nwchemgit/nwchem/wiki/Compiling-NWChem#how-to-linux-platforms