ORCA is an ab initio, DFT and semiempirical SCF-MO quantum chemistry package. Detailed infromation about the package is available on the software home page:

https://orcaforum.cec.mpg.de/

Orca-example.inp

! BP86 def2-SVP Opt 
# BP86 is here the method (DFT functional), def2-SVP is the basis set and Opt is
# the jobtype (geometry optimization). Order of the keywords is not important.

*xyz 0 1
H 0.0 0.0 0.0
H 0.0 0.0 1.0
*

Create a PBS script orca-serial.pbs

#PBS -q debug16core
#PBS -l nodes=1:ppn=16

module load gcc/4.6.3 openpmi/1.6.5 orca

orca orca-example.inp >orca-serial.log

And to submit the job to the queue

razor-l1:pwolinsk:/ORCA-examples$ qsub orca-serial.pbs

This will launch a serial job running on one core of one node in debu16core queue.

Add the %pal nprocs=32 end directive block to the orca-example.inp file, to instruct orca to launch 32 processes across all nodes assigned to the job.

! BP86 def2-SVP Opt 
%pal
nprocs 32 
end
# BP86 is here the method (DFT functional), def2-SVP is the basis set and Opt is
# the jobtype (geometry optimization). Order of the keywords is not important.

*xyz 0 1
H 0.0 0.0 0.0
H 0.0 0.0 1.0
*

Rename the orca-serial.pbs script to orca-parallel-32.pbs and modify the nodes parameter nodes=2 to ask the scheduler for 2 nodes instead of 1. Also specify the full path to the orca executable /share/apps/orca303linux_x86-64/orca

#PBS -q debug16core
#PBS -l nodes=2:ppn=16

module load gcc/4.6.3 openpmi/1.6.5 orca

/share/apps/orca_3_0_3_linux_x86-64/orca Orca-serial.inp >Orca-parallel-32.log

And to submit the job to the queue

razor-l1:pwolinsk:/ORCA-examples$ qsub orca-parallel-32.pbs

This orca job will start 16 processes on the first node and 16 more processes on the second node assigned to the job.