beta-Si3N4 particles are thought to be nucleation sites for silicon in multicrystalline silicon (mc-Si) ingots for PV applications. The orientation relationship (OR) between Si and beta-Si3N4 has been investigated by transmission electron microscopy (TEM). The following OR was found by analyzing diffraction patterns from a site specific sample prepared by focused ion beam (FIB) [0001](beta-Si3N4) vertical bar vertical bar [1 (1) over bar 1](st) ((4) over bar 5 (1) over bar 0)(beta-Si3N4) vertical bar vertical bar [1 (1) over bar 1](st) The beta-Si3N4 particle was identified as a likely nucleation site based on the grain boundaries (GB) extending from it. It was shown that these GBs were Sigma 3 boundaries. The nucleation process was discussed as a source for formation of twins in mc-Si. (C) 2018 Elsevier B.V. All rights reserved.