“…1 are for oxides. Recently, the structures of a number of binary and ternary Si nitrides have been reported: ¢~-Si3N 4 (Marchand, Laurent, Lang & Le Bihan, 1969;Kohatsu & McCauley, 1974), flSi3N 4 (Borgen & Seip, 1961), LiSi2N 3 (David, Laurent, Chariot & Lang, 1973), MgSiN 2 (David, Laurent & Lang, 1970), MnSiN 2 (Winterberger, Marchand & Maunaye, 1977) and Si2N20 (Idrestedt & Brosset, 1964). In these compounds SiN 4 tetrahedra (SiN30 in the last) are joined by a bridging N atom, with the Si-N-Si angle equal to ,-,120 °.…”