Installing ORCA on macOS Arm64

ORCA is a quantum chemistry program for molecular electronic structure calculations, developed and maintained by Frank Neese’s research group at the Max-Planck-Institut für Kohlenforschung in Mülheim an der Ruhr, Germany. It supports density functional theory (DFT), coupled-cluster theory, semi-empirical methods, and more.

Version 6.0.0, released in August 2024, is a major redesign (see the foreword to its release ). This guide covers installing it on macOS with Apple Silicon (M1, M2, etc.), including Open MPI setup for parallel calculations.

# Installation

# Getting the files

To get started, download the ORCA package from the official ORCA download page . Note that you’ll need a registered account to access the download—registration is free if you don’t have an account yet.

For macOS on Arm64, the download page lists two options (both containing pre-compiled binaries linked to Open MPI 4.1.1):

1. ORCA 6.0.0, MacOS X, Arm64, Installer Version: Extracts, installs, and adds ORCA to your PATH automatically.
2. ORCA 6.0.0, MacOS X, Arm64, .tar.bz2 Archive: Manual extraction and PATH setup, but more control over the installation location.

This guide uses the Installer Version, which downloads as orca_6_0_0_macosx_arm64_openmpi411.run.

# Setting file permissions

Before running the installer, make it executable:

cd ~/Downloads
chmod +x orca_6_0_0_macosx_arm64_openmpi411.run

# Running the installer

Run the installer from the same directory:

$ ./orca_6_0_0_macosx_arm64_openmpi411.run

Creating directory orca_6_0_0
Verifying archive integrity...  100%   MD5 checksums are OK. All good.
Uncompressing ORCA 6.0.0 Installer ...  100%

By default, this operation installs the ORCA binaries in the directory /Users/<username>/Library/Orca/, where <username> is your system’s user.

# Setting the PATH

The installer should automatically add ORCA to your system’s PATH. Verify by running:

$ orca

This program requires the name of a parameterfile as argument
For example ORCA TEST.INP

If you see this output, ORCA is installed. You can also confirm by checking your .zshrc (macOS ships with zsh by default) for a line like:

# ORCA 6.0.0 section
export PATH=/Users/<username>/Library/orca_6_0_0:$PATH

If this line is missing, add it manually, pointing to the correct installation directory. Save the file and restart your terminal.

# Parallelization with Open MPI

To run calculations in parallel, ORCA needs Open MPI.

Download Open MPI 4.1.6 from the official Open MPI page . The file is openmpi-4.1.6.tar.gz.

Before compiling, install the Fortran compiler via Homebrew :

brew install gcc

Unpack and prepare Open MPI for compilation. This example installs it in a dedicated folder in the home directory:

# Create a directory for Open MPI
$ mkdir $HOME/openmpi
$ cd $HOME/openmpi

# Move the downloaded file and extract it
$ cp ~/Downloads/openmpi-4.1.6.tar.gz .
$ tar -xzvf openmpi-4.1.6.tar.gz
$ cd openmpi-4.1.6

Compile Open MPI with Fortran support and the flags needed for ORCA:

./configure --prefix=$HOME/openmpi --without-verbs --enable-mpi-fortran --disable-builtin-atomics
make all
make install

./configure --prefix=$HOME/openmpi --without-verbs --enable-mpi-fortran --disable-builtin-atomicsC LDFLAGS="-ld_classic"

Compilation takes time. To speed it up, use multiple cores with the -jN flag:

make -j4 all
make -j4 install

After compilation, create a symbolic link to make Open MPI accessible system-wide:

sudo ln -s $HOME/openmpi/lib/libmpi.40.dylib /usr/local/lib/libmpi.40.dylib

Update the PATH and LD_LIBRARY_PATH in your .zshrc (or .bash_profile if using bash):

export PATH=$HOME/openmpi/bin:$PATH
export LD_LIBRARY_PATH=$HOME/openmpi/lib:$LD_LIBRARY_PATH

Run source ~/.zshrc (or restart your terminal), then verify:

$ mpirun --version

mpirun (Open MPI) 4.1.6

Report bugs to http://www.open-mpi.org/community/help/

If you see this output, Open MPI is ready.

# Testing

Verify the setup by running a simple calculation. Create a folder for the test files:

# Navigate to the desktop
$ cd ~/Desktop

# Create a new folder for the test
$ mkdir orca_test
$ cd orca_test

# Create an input file for the calculation
$ touch water.inp

Add a basic Hartree-Fock (HF) calculation on a water molecule using the Def2-SVP basis set (from the official ORCA tutorial ):

!HF DEF2-SVP

* xyz 0 1
O   0.0000   0.0000   0.0626
H  -0.7920   0.0000  -0.4973
H   0.7920   0.0000  -0.4973
*

Save the file and run ORCA in serial mode:

$ orca water.inp

                                 *****************
                                 * O   R   C   A *
                                 *****************

--- truncated output ---

Timings for individual modules:

Sum of individual times          ...        0.245 sec (=   0.004 min)
Startup calculation              ...        0.081 sec (=   0.001 min)  33.0 %
SCF iterations                   ...        0.114 sec (=   0.002 min)  46.5 %
Property calculations            ...        0.050 sec (=   0.001 min)  20.6 %
                             ****ORCA TERMINATED NORMALLY****
TOTAL RUN TIME: 0 days 0 hours 0 minutes 0 seconds 302 msec

If the output ends with ORCA TERMINATED NORMALLY, the serial setup works. Next, test parallel execution by adding a %PAL block that specifies the number of processes. Update water.inp:

!HF DEF2-SVP

%PAL NPROCS 4 END

* xyz 0 1
O   0.0000   0.0000   0.0626
H  -0.7920   0.0000  -0.4973
H   0.7920   0.0000  -0.4973
*

For parallel runs, use the full path to the ORCA executable (replace <username> with your macOS username):

$ /Users/<username>/Library/orca_6_0_0/orca water.inp

           ************************************************************
           *        Program running with 4 parallel MPI-processes     *
           *              working on a common directory               *
           ************************************************************

--- truncated output ---

Timings for individual modules:

Sum of individual times          ...       17.403 sec (=   0.290 min)
Startup calculation              ...       16.408 sec (=   0.273 min)  94.3 %
SCF iterations                   ...        0.721 sec (=   0.012 min)   4.1 %
Property calculations            ...        0.275 sec (=   0.005 min)   1.6 %
                             ****ORCA TERMINATED NORMALLY****
TOTAL RUN TIME: 0 days 0 hours 0 minutes 17 seconds 708 msec

If the output confirms 4 parallel MPI processes and terminates normally, both ORCA and Open MPI are working.