Phosphides of the B31 (MnP) Structure Type.

Abstract : The mono-phosphides of Cr, Mn, Fe, Co, W, and Ru crystallize in the B 31 (MnP) structure type. The unit cell dimensions of these phosphides were measured, and the structures of MnP, FeP and CoP were determined accurately by single-crystal methods. Some data for unit cell variations accompanying isomorphous substitution are presented and discussed. Among the phosphides, CoP is the only B 31 (K) phase. The author found complete solid solubility of FeP, MnP and CrP in CoP. The compositions for the alloys with c/b = 3 to the 1/2 power were approximately: Co(0.6) Fe(0.4)P, Co(0.8) Mn(0.2)P, and Co(0.87)Cr(0.13)P, which implies that the number of electrons is roughly constant at this c/b ratio. The unit cell dimensions for B 31 phases are dependent on electronic factors. The data from the structure determinations did not indicate any marked structural difference between B 31 (1) and B 31 (k) phases.