The structures of WTe2 and a high-temperature monoclinic polymorph of MoTe2 have been solved by Patterson methods. Single crystals were grown by vapor transport methods. Cell dimensions, as measured on precession photographs, are for WTe2, a=6.282/~, b= 3.496/~, c= 14"073 A. Similarly for MoTe2, a=6.33 A, b=3.469/~, c=13.86/~, B=93°55. Intensities were measured for both crystals from zero-and first-level Weissenberg photographs. WTe2 and MoTe2 are given the space groups Pnm21 and P21/m, respectively. Minimum function maps prepared by a superposition method gave approximate trial structures for both compounds which were refined by least-squares methods to R values of 12.5 % and 13-9 % for WTe2 and MoTe2 respectively. Both compounds are layer structures with double sheets of tellurium atoms bound together by interleaving metal atoms. An off-center positioning of metal atoms in the tellurium octahedra buckles the tellurium sheets and allows metal atoms in adjacent octahedra to approach each other. Each metal atom, therefore, has eight neighbors, six tellurium atoms and two metal atoms, and a significant amount of metal-metal bonding is introduced.
The crystal structures of the isostructural compounds, NbTe2 and TaTe2, have been solved by Patterson methods. Single crystals were grown by vapor transport methods. Cell dimensions, as measured on precession photographs, are for NbTe2, a= 19.39, b= 3.642, c=9.375 •, r= 134°35 ', and for TaTe2, a= 19-31, b= 3-651, c=9-377 A, r= 134 ° 13'. Both compounds belong to the space group C2/m.Refinement of the hOl intensities by least-squares methods gave R values of 13 Yo and 10 Vo for NbTe2 and TaTe2 respectively. The compounds are layer structures with distorted octahedral coordination of the metal atoms by tellurium atoms. The distortion is a response to a pattern of metal-metal bonding in which the metals are grouped into triple rows parallel to the y axis. This grouping puts two-thirds of the metal atoms in distorted octahedra and one-third in relatively regular octahedra.
Ausgehend von dem cis‐ (I) oder dem trans‐ Chlorodiammin‐1‐methylcytosin‐N3‐Pt(II)‐Komplex (V) werden durch Umsetzung der Aquo‐Analogen in situ mit 9‐Methyladenin die9‐Methyladenin‐N7‐ und 9‐Methyladenin‐N′‐Derivate (II) und (III) bzw. (VI) und (VII) sowie das Dimere (IV) oder (VIII) gebildet.
Mineralogical analyses were made of the day, silt, and sand fractions of the Podzols Hiawatha loamy sand and Hiawatha sand. The layer silicates show chemical weathering as a function of depth in both soils. A high charge dioctahedral montmorillonite was dominant in all fractions (-5g) of the -'/2 horizon and its origin was attributed to weathering of an interstratified vermiculite-chlorite similar to that in the B2 horizon. The 2 to 0.2/z fraction of the Hiawatha loamy sand B2 horizon contains 14 percent chlorite and 18 percent vermiculite with no montmorillonite, and the Hiawatha loamy sand .42 horizon contains 33 percent montmorillonite with little interstratified chlorite-vermiculite. Quartz also showed a soil depth function in the fine silt. It is higher in amount in the ,42 than the Bz horizon, attributable to its relative stability in the Podzo1-42. Below the Bz it drops markedly in amount, attributable to a difference in silt deposition.The similarity of ratios of resistant heavy minerals (greater than 2.95 sp. gr.) in different horizons indicates uniform origin of the sand fractions of these soils. Light mineral contents in the sand fractions for all analyzed horizons are also similar. However, particle size data indicate silt and possible clay addition to both the//2 and//2 horizons.Depth functions in these soils are developed to a marked extent, apparently owing to (1) low amount of fine fraction originally present for weathering, (2) greater amount of water cycled through the 212 than the B2 horizon, (3) rapid and frequent cycling of available water owing to coarse texture, and possibly (4) effects of podzolization. The Omega, Ahmeek, and Iron River soils of northern Wisconsin also showed a similar though not so marked tendency to accumulate montmorillonite in the z12 horizon.
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