“…Cr,BTO13 I,Mr=566.56,cubic,F713c,a =12.214(1)~, V=1822.1(5) /~ 3, Z=8, Introduction. Boracites, M3B 7013 X (M = bivalent metal ion, X = halogen ion), tend to undergo structural phase transitions (Schmid, 1965;Nelmes, 1974;Toledano, Schmid, Clin & Rivera, 1985). A structural feature of particular interest is the environment of the metal ions because it is relatively invariant with respect to the substitution of other metal and halogen ions whereas it changes strongly during phase transitions.…”