Surlace Scmnce 168 (1986) 204 211 North-Holland Amsterdam ELECTRON ENERGY-LOSS SPECTROSCOPY OF Ni2Si: VALENCE COLLECTIVE EXCITATION AND STRUCTURAL PROPERTIES* M G BETTI, C RINALDI, P SASSAROL1, L SORBA and S NANNARONE l)tparttrnento dt Ft~ua, I_hut er~lta ch Roma La ~aptenza , 1d)0185 Rome ltal~ M DE CRESCENZI l)qmrttnwnto dt f't~ua Unller~tta de I Aquzla I~57100 l.' lqtttla, ltal~ and U DELPENNINO, C MARIANI and S VALERI l)tpart.nento dt ktstc a Unit etstta dt Modena l~il I00 Modena, ltal~ t~,ctt.l~utt 10 Junt. 198q at.ct.pted Ior pubhcatlon 12 lul~ lt)Sq NbSI x~ds ',tu&cd b'~ ult.~_tron t.nurgv-lo,,,, spt ~.trosuop~ m th,~ xalt.nct, and t_oiu lt.,,t.I (N~ NI~ , and L 3 x) cxclt,ltltm region The xalt.nt.t, loss stru~.ture was ~_orrt.latud xslth the slh~_ld~. ~_[t_t_llOnlc prop~.rllt.~, Fhc experlnlental radial dlMrlbutlon [tlnLllOll dlOtllld a NI ,110111 \~.,i ~, ,.'datdlncd b\ l~ounur analyzing the extended loss sp~_utrum ,lbo~t. tilt. Ni M, , t~dgu 1. Introduction The transltum-metal-sfllCOn compounds haxe been widely studied [1] m the last years because of thmr technologmal interest In this paper we present ,m experimental work on NbSI bulk samples based on electron energy-loss spectroscopy (EELS) m the regum ol ~alence and core level excltanon The results reported here must be xmwed as part ol a wqder program whose hnal goal is the stud~ ol the N1 Si interlace Prexums papers on Pd-Sl (interlace) [2] ,rod Pd,SI (bulk) [3] belong to thl~ program It is worthwhde stressing the posslbllmes oflered by EELS m simul- taneous studies ol both the electromc structure (surlace and x olume) and the structural propertms [4] We lound that the loss structure ol NI.S1 is characterized by a shflt ol the Work partially supported b,: Gruppo Nazumalu dl Strutturd dt.lla Mdturhi dcl ('NR (1(139-6028/86/$03 50 © Elsevier Science Pubhshers B V (North-Holland Physics Pubhshmg DlvNon)