X-RAY AND NEUTRON DIFFRACTION STUDIES OF METALS AND ALLOYS.
Final rept. 1 Jan 66-30 Aug 69,
MASSACHUSETTS INST OF TECH CAMBRIDGE
Pagination or Media Count:
X-ray crystal structure work on the M phase Nb-Ni-Al, was completed. This orthorhombic structure Pnam, 52 atoms shows close relationships to the P and nu phases. The crystal structure of the nu phase, Mn81.5Si18.5, was determined and refined to a high degree of precision. This is the most complex structure yet determined in this program, having 186 atoms in an orthorhombic unit cell Immm. This structure, too, is closely related to the P phase. A third orthorhombic structure Pnnm, 74 atoms has been determined for the Q X, Y phase in Mn-Co-Cr. A rough trial structure was obtained for the monoclinic K phase, Fe-Mn-Si. The structures of the monoclinic I phase V-Ni-Si and the S phase Mn-Co-Si are probably identical. A new scheme for coding layered tetrahedrally close-packed structures was developed. Reinterpretation of polarized-beam neutron diffraction data for 85 ordered VFe, 46.7 at Fe, has given an improved value for the Fe spin, S sub Fe 0.368 plus or minus .024 the spin on the vanadium is zero within experimental error. Previous indications of a highly aspherical 3d shell on ion were not substantiated. Attempts to prepare single crystals of sigma CoV for polarized beam single crystal neutron studies were unsuccessful. Author