how to change particle density after restart

Hi all,

I am seeking for an approach to changing the particle density from 2.6e3 kg/m3 to 2.6e6 kg/m3 after using my restart file. Does anyone know which command should I use for realizing this?

We normally set the particle density in command "fix particletemplate/sphere". As I see from the documentation, no fix_modify command can be applied to "fix particletemplate/sphere". So I want to figure out whether there exists a method that we can change the particle density during modelling?

Thank you very much!

Best,
Rachel