OPT-PROD/PROP of material

Dear experts,
If I set a geometry region with a compound (I call it material C,just mixed with material A and B), material A have optical property and material B not, actually the two material does not react each other. Now I set OPT-PROD and OPT-PROP, the option “Mat” “to Mat” ,should I use the material A or material C?

For example ,just see the picture. LiF and ZnS mixed together and set as geometry region’s material, only ZnS have optical property, then how to set OPT-PROD/PROP’s option “Mat” and “to Mat”?
“ZnS” or “LiFZnS” or set two card “ZnS”,“LiF” respectively?

Dear @xiongbp,

You must assign optical properties to the final composite materials that you will use in the simulation. In your case, if the materials LiF and ZnS are not used in any region, then assigning optical properties to them will not have any effect. You must instead assign optical properties to the composite material LiFZnS as it will actually be assigned to a region. Also, to be clear, there’s no need to assign optical properties to any component material making up LiFZnS.

Dear @blefebvre ,
I have understand it and thank you for your help.