Sometime, I'm calculate CaMnO3 in site 2 unit cell which Quantum Espresso show error 'mpirun noticed that process rank 3 with PID 2783 on node SRL exited on signal 9 (Killed)'
As i know this is a memory problem, you dont have enough memory (free space) in which your calculations may complete. You may decrease the no of KPOINTS or you may use more than 1 nodes for your calculations.