Permodelan localized surface plasmon resonance (LSPR) paduan emas-perak AgxAu100-x (wt%) dengan x=0, 20, 40, 60, 80, dan 100 pada nanopartikel bentuk batang menggunakan metallic nanoparticle boundary element method (MNPBEM) = Modelling of localized surface plasmon resonance lspr alloy AgxAu100-x (wt%) with x=0, 20, 40, 60, 80, and 100 on rod shape using metallic nanoparticle boundary element method (MNPBEM)