# Issues about ScatterMatrixXS and DiffusionCoefficient **URL:** https://openmc.discourse.group/t/issues-about-scattermatrixxs-and-diffusioncoefficient/1901 **Category:** User Support **Created:** [April 6, 2022, 1:45pm UTC](https://openmc.discourse.group/t/issues-about-scattermatrixxs-and-diffusioncoefficient/1901 "2022-04-06T13:45:12Z") **Posts on this page:** 1 **Page:** 1
### Author: ![LagrangeW](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/lagrangew/32/2246_2.png) [@LagrangeW](https://openmc.discourse.group/u/LagrangeW) #### Post date: [April 6, 2022, 1:45pm UTC](https://openmc.discourse.group/t/issues-about-scattermatrixxs-and-diffusioncoefficient/1901/1 "2022-04-06T13:45:12Z")
Hi everyone, I was simulating a homogeneous SFR model, trying to export a 10-group (equal-lethargy structure from 0.418eV-14.7MeV) scattering XS matrix. Considering the isotropic scattering of fast reactor, I set the Legendre\_order to 3, then I got a csv file with a form like material | group in | group out | legendre | nuclide | mean 3 1 1 P0 total 0.121986159 3 1 1 P1 total 0.063974833 3 1 1 P2 total 0.047618702 3 1 1 P3 total 0.032470687 Is the XS data each line here means “each legendre component” or "corresponding XS data with Pn approximation” ？ Best regards! Weixiang Wang