If it is a multi-user opens the root account, enter in a terminal: vim / etc / profile to enter the edit profile. In the last line with source /opt/software/impi/mpivars.sh is lammps on this server storage environment, and then: wq (save and exit), on it.
If only a single account would like to achieve this effect, landed a personal account, enter in a terminal: vim ~ / .bashrc add this line to save at the last exit on it.