Support for additional lanthanide ions: can users add custom Ln³⁺ definitions?

[jjjjjqt]

Hi maintainers,

I’m working with lanthanide(III) ions (Ln³⁺) and noticed that the project’s supported lanthanide ions are not complete. When I try to specify a lanthanide ion that is not currently supported (e.g., Nd³⁺), the program rejects it as “unsupported” / fails to proceed due to missing ion definitions.

My question is: can users extend the lanthanide ion support by adding custom definitions?

Specifically, I’d like to understand the intended extension path and the required pieces:

1. Where is the “ion/element support list” defined (hard-coded registry, config file, parameter database, etc.)?
2. What is the minimal set of data required to add a new Ln³⁺ ion?
   • (examples) basis/ECP definitions, force-field parameters, ionic radius, coordination preferences, charge state handling, etc.
3. Is the limitation purely an input validation/whitelist issue, or are there deeper missing parameters that the workflow depends on?
4. If custom ions are supported, is there a recommended format/example (e.g., how La³⁺ is represented) that I can follow?
5. If custom ions are not supported today, would you accept a PR that adds support for additional Ln³⁺ ions (Nd³⁺/...) in the same way existing lanthanides are implemented?

Thanks for your guidance — I’m happy to follow the project’s preferred approach and contribute improvements if that’s welcome.

[jjjjjqt]

@UnixJunkie @xrobin @mestia @zrt