Questions about k_method parameter and scattering order in c5g7.lua

[hityyds]

Hello,

I encountered two issues while working with the c5g7.lua benchmark and would appreciate your guidance.

1. Missing k_method Definition
When executing the c5g7.lua benchmark using:
mpirun -np 12 ~/OpenSN/opensn/build/lua/opensn -i c5g7.lua
I received an error:
**!**ERROR**!** LuaError: c5g7.lua:12: bad argument #1 to 'find' (string expected, got nil)
The problematic code is:
if string.find(k_method, "scdsa") or string.find(k_method, "smm") then
I couldn't find any declaration/definition of k_method in c5g7.lua or its imported scripts. Is k_method supposed to be set via command-line parameters? The error disappeared after I manually defined k_method in the script.

2. Scattering Order Mismatch Warning
When creating a custom script for an isotropic scattering problem – mirroring the c5g7.lua structure and explicitly setting scattering_order = 1 – I encountered:
**WARNING** InitializeMaterials: Cross-sections on block "1" has a lower scattering order (0) than the simulation (1).
This confuses me because c5g7.lua explicitly sets scattering_order = 1. Why does this benchmark use scattering_order=1 for what appears to be isotropic scattering? Shouldn't isotropic scattering require scattering_order=0? How does this parameter interact with material definitions?

Thank you for your time and expertise!