Very good software to simulate crystal structures and their diffraction patterns. What is available is very efficient. I am not 100% happy about features in lists of diffraction peaks and in the appearance of exported figures, but that may also be a problem due to a wrongdoing user. Of course it depends on what you want to do. I would be happy having stereographic projections. We also use here putting several crystals in one image to analyse orientation relationships. For that we use Vesta (free to use; which is also very powerful). In fact we use both softwares in parallel.

As Andreas said above, what do you want it for? For visualization? Mercury is free and can also simulate powder patterns. Vesta is very powerful and also free. If you can be more specific on what you want to do with the software, then we can point out the capabilities of each to do what you want.

I would like to upload xyz coordinates of nanoclusters and simulate x-ray diffraction patterns and possibly electron diffraction patterns. Thanks to all for their advice.

Also I would prefer software compatible with macOS.

To me the names of the software indicate that they all assume crystals, i.e. a periodic and infinite arrangement of atoms, ions or molecules. This means that single clusters you can use but you need to define a periodicity which is not predictable by the cluster itself.

There are certainly software packages available which are not based on the assumtion of crystals. They use the x,y,z and calculate the intraction without periodicity. You should look then for the term radial distribution function. Such software packages are used to investigate partially crystalline phases like glass or x-ray amorphous materials , i.e. where the volume is comparatively small compared to the surface.

I have a plan to include the RDF.

If you only use these clusters and you dont produce crystals the upper mentioned programs are possibly useless. Then RDF is your choice!

Crystal maker can deal with molecules (I have rarely used that option), but I do not know by heart whether resonable diffraction patterns can be simulared with the diffraction tools associated with Crystalmaker.

Confirmation: upon useing the molecule option (e.g. converting a part of a crystal into am molecule), the powder diffraction/single crystal modules are dead (version 2.7.7)