Solving common issues

Fixing file names

If you get errors like:

[file orca_main/run.cpp, line 9905]: Cannot open input file:

please check your file type, maybe you are calling input.inp, but it was saved as input.inp.txt or something else.

When using windows, we recommend using Notepad++ instead of the regular Notepad to avoid problems when writing and reading.

Assigning PATH variables

A quite common initial source of error when trying to run ORCA is that your PATH variables are not set. The PATH and LD_LIBRARY_PATH are variables that your OS use to find where the programs and libraries are. Here some quick info on how to set them correctly:

Linux and MAC

Type the commands bellow to add the correct variables to the .bash_profile file and source it. Nothing will happen, but if everything is right, "orca" can now be called as a simple command.

  • ORCA:

echo 'export PATH=path-to-ORCA:$PATH; export LD_LIBRARY_PATH=path-to-ORCA:$LD_LIBRARY_PATH'  >> ~/.bash_profile
source ~/.bash_profile

replacing path-to-ORCA to where the orca folder is on your system, e.g, /home/username/orca.

  • OpenMPI:

echo 'export PATH=path-to-MPI/bin:$PATH; export LD_LIBRARY_PATH=/path-to-MPI/lib:$LD_LIBRARY_PATH'  >> ~/.bash_profile
source ~/.bash_profile

replacing path-to-MPI to where the OpenMPI folder is on your system, e.g, /home/username/openmpi.


The MAC installer installs ORCA by default in /Users/<username>/Library/Orca/.

Windows 10

  • ORCA:

    The windows installer will put the ORCA folder in C:\orca, and you need to set the PATH there to find it. To do that, follow the steps bellow:

    1. Click on the search button or hit the Windows/Super key and type "PATH":

    2. Click on the "Environment Variables..." button:

    3. Find the row where "Path" is and click on edit:

    4. A new windows will open, there click on "New" and add "C:\orca":

    5. Click OK and the changes are saved. Now type "orca" on the prompt to see if the program is called (will return an error message if there is no input).

  • OpenMPI:

    You can install following instructions from the ORCA manual or the OpenMPI. Probably the best solution is to use Cygwin to simulate a Linux environment and run it from there.


    Do not forget to set the PATH and the LD_LIBRARY_PATH using the same instructions as above.

Using OpenMPI

Don't try to run:

mpirun -np 4 orca

like with other software, ORCA will take care of it if your have the !PAL keyword set.

Error from older files

Sometimes calculations fail because there are files from a previous orca run in the folder and then orca tries to read from them, but actually you just want to start a totally new calulation, so those files have to be deleted manually beforehand!

Still having trouble?

  • Check that the PATH variables are set correctly.

  • Check if file names are correct.

  • Go to the ORCA forum, take a look at the previous topics and ask your questions 😉!