MultiWFN

This ia a free and very feature rich implementation of Bader's QTAIM analyses.

The source and executables can be obtained from https://multiwfn.codeplex.com
I have gotten the OS X (Yosemite) running by following all of the install instructions, including extracting the libdislin_d.10.dylib from the source download and installing it in /usr/local/lib
You can read about some of the benefits of using this code in the comments at the end of http://www.ch.imperial.ac.uk/rzepa/blog/?p=14272 --Rzepa (talk) 14:53, 16 July 2015 (BST)

El Capitan OS X and macOS Sierra

One of the steps in the above is downloading and installing a OpenMotif graphics library from http://www.ist-inc.com/motif/download/openmotif_download.html Unfortunately, the latest OS X supported is 10.5, and "there are no plans" to build it for later versions. In particular, the installer needs the following procedure when using El Capitan.

Back up your main drive
Reboot your computer whilst simultaneously holding the Cmd ⌘ and R keys to enter recovery mode.
Click the utilities menu and select terminal.
Type csrutil disable and press return
Restart
Using the terminal program, type: xcode-select --install to install the Xcode command line tools needed below.
Now download the OpenMotif library as http://www.ist-inc.com/motif/download/motif_files/openmotif-compat-2.1.32_IST.macosx10.5.dmg and double click to mount the package.
Download Pacifist from https://www.charlessoft.com
From the OpenMotif folder, drag the .pkg file onto Pacifist
Select the contents of OpenMotif-compat-2.1.32.pkg and from the file menu install files to default locations.
You can now reverse 4 above using csrutil enable and restart
Ensure you have XQuartz installed http://www.xquartz.org
Download MultiWFN from eg https://multiwfn.codeplex.com and move the folder to the /applications area (you might want to rename it simply Multiwfn first).
In this folder, you will find a file called libiomp5.dylib
Using the terminal program, type : cd /applications/multiwfn
Using the terminal program, type: sudo cp libiomp5.dylib /usr/local/bin/. (you will have to provide your password at this stage)
Download https://www.codeplex.com/Download?ProjectName=multiwfn&DownloadId=1525622 and rename the resulting folder e.g. /applications/ws
1. using the terminal program:cd /applications/ws and then: sudo cp libdislin_d.10.dylib /usr/local/lib/.
2. using the terminal program: sudo install_name_tool -change libiomp5.dylib /usr/local/bin/libiomp5.dylib /applications/multiwfn/multiwfn
3. Using the terminal program: sudo install_name_tool -change libdislin_d.10.dylib /usr/local/lib/libdislin_d.10.dylib /applications/multiwfn/multiwfn
4. verify, using the terminal program: sudo otool -L /applications/multiwfn/multiwfn
You will have to edit the file .profile in /users/name (where name is your account name) to include the line: export KMP_STACKSIZE=64000000
In the /applications/multiwfn folder, edit the file settings.ini using a text editor (Textedit or other). There are a number of tweaks you can apply here, the most important of which is to change the parameters below the line //Below are the parameters about system environment
1. change: threads =8 (if 8 is the number of processors on your system). Make sure the file is saved with Unix LFs (the default is Windows, and OS X might not respond correctly).
In terminal, type: cd /applications/multiwfn and then ./multiwfn or simply double clicking the file in Finder.
If all has worked you should now get a simple prompt:

 Multiwfn -- A Multifunctional Wavefunction Analyzer (for MacOS X)
 Version 3.3.8, release date: 2015-Dec-1
 Project leader: Tian Lu  (Beijing Kein Research Center for Natural Sciences)
 Citation of Multiwfn: Tian Lu, Feiwu Chen, J. Comp. Chem. 33, 580-592 (2012)
 Multiwfn official website: http://Multiwfn.codeplex.com
 Multiwfn official forum (in Chinese): http://bbs.keinsci.com
 Bug reporting, question and suggestion, please contact: Sobereva@sina.com
 ( The number of threads:  8   Current date: 2016-02-04   Time: 13:41:27 )
 
 Input file path, for example E:\Haiyore!Nyaruko-san\Nyaruko.wfn
 (Supported types: .wfn/.wfx/.fch/.31/.chg/.pdb/.xyz/.cub/.grd/.molden, etc.)
 Hint: To reload the file last time used, simply input the letter "o". Input such as ?miku.fch can open miku.fch in the same folder of the file last time used

Note added 13/02/2017

In the latest download of this program, steps 14-17 are no longer necessary. The file libiomp5.dylib is no longer present in the folder. --Rzepa (talk) 10:01, 13 February 2017 (UTC)

Note added 25/11/2017

Using XQuartz 2.7.11 to visualize outputs fails. To fix it, execute the following two commands from a terminal--Rzepa (talk) 11:53, 25 November 2017 (UTC)

   sudo mv /opt/X11/lib/libXt.6.dylib{,.bak} 
   sudo cp /opt/X11/lib{/flat_namespace,}/libXt.6.dylib