Dmol3 only works on one core on HPC

We are using Dmol3 to model chemical reactions on Ni surface, and it is weird that Dmol3 can only work on one core. When we use multiple cores, the job runs for around 2 hours then crash with the below error:

slurmstepd: error: Detected 1 oom-kill event(s) in StepId=7297519.0 cgroup. Some of your processes may have been killed by the cgroup out-of-memory handler.

srun: error: node051: task 0: Out Of Memory

I_MPI_JOB_TIMEOUT = -1 second(s): job ending due to startup timeout

DMol3.pl message: DMol3 job finished in 2 hr 12 min 11 sec.

Also, when we are trying to use multiple cores, the memory goes very high. This problem only happens when we are using HPC that we can use single PC based for multiple cores without problem. 

Appreciate if there is nay suggestion on this.

Xiaolei