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Synchrotron Radiation Applied to Computer Indexing

  • Gordon S. Smith (a1), Quintin C. Johnson (a1), David E. Cox (a2), Robert L. Snyder (a3), Deane K. Smith (a4) and Allan Zalkin (a5)...


Synchrotron radiation was used to obtain a high-resolution powder diffraction pattern of the high-density form of BeH2, a material whose unit-cell dimensions have not previously been determined. The observed d-spacing values were presented to three different computer indexing programs. All three programs returned as best solution a body-centered orthorhombic unit cell with a = 9.082, b = 4.160, c = 7.707 Å and V = 292 Å3. Interpretation of the three-dimensional Patterson led to 12 BeH2 molecules per unit cell; thus, the theoretical density is 0.755 g/cm3. The molecular structure is based on a network of corner-sharing BeH4 tetrahedra rather than flat, infinite chains with hydrogen bridges previously assumed.



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2. Brendel, G.O., Marlett, E.M. and Niebylski, L.M., “Crystalline Beryllium Hydride”, Inorg. Chem. 17., 3589 (1978).
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5. Werner, P.-E., Eriksson, L. and Westdahl, M., “TREOR. A new in-Exhaustive Trial-and-Error Powder Indexing Program for All Symmetries”, J. Appl. Cryst. 18, 367 (1985).


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