==== ORCA ====

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/


=== Example input file ===
Orca-example.inp
<code>
! 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
*
</code>

=== Serial job ===
Create a PBS script orca-serial.pbs
<code>
#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
</code>

And to submit the job to the queue
<code>
razor-l1:pwolinsk:/ORCA-examples$ qsub orca-serial.pbs
</code>

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


=== Parallel job ===
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.

<code>
! 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
*
</code>

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/orca_3_0_3_linux_x86-64/orca**

<code>
#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
</code>

And to submit the job to the queue
<code>
razor-l1:pwolinsk:/ORCA-examples$ qsub orca-parallel-32.pbs
</code>

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