Introducing compound not defined in G4

Hi there, I am looking to introduce Gadolinium Sulfate (Gd2O12S3) in a certain volume. I looked in the book for application developers but could not find it. So my question is: can I introduce, in the volume, the right proportion of Gd, O and S separately to simulate the Gadolinium sulfate?

examples/basic/B3 :

Hi Michael, thank you very much for the reply.
I completely forgot to look up the examples, sorry about that.

Hi @maire. So I have managed to define the new compound correctly but now I get this error message when trying to run the application.

physicsList->setCut() start.

-------- EEEE ------- G4Exception-START -------- EEEE -------
*** G4Exception : GeomMgt0002
issued by : G4Region::ScanVolumeTree()
Logical volume
does not have a valid material pointer.
A logical volume belonging to the (tracking) world volume must have a valid material.Check your geometry construction.

*** Fatal Exception *** core dump ***
**** Track information is not available at this moment
**** Step information is not available at this moment

-------- EEEE -------- G4Exception-END --------- EEEE -------

*** G4Exception: Aborting execution ***

I don’t know how to define the material as a valid material or even if it is possible to do so.

Thanks in advance.

The answer is also in B3 :
Or any other example …

Thank you for your time Michel.