Stable orthorhombic phase

These crystal modifications differ in their molecular and crystal structures as well as in their physical properties. Many types of crystalline modifications are reported, including a stable orthorhombic phase and metastable monoclinic phase for PE a, and y forms for isotactic polypropylene (/-PP) trigonal and orthorhombic phases for polyoxymethylene a and y forms for Nylon 6 and others. Poly(vinylidene fluoride) (PVF), for example, appears in at least four types of crystalline modification (Lovinger, 1985 Dunn Carr, 1989). 

The authors report that the particles have a unusual metastable cubic zinc-blende phase instead of the more stable orthorhombic phase (Fig. 13). The phase change of SnS nanocrystals from orthorhombic to zinc-blende was also recently reported by Jin et They employed a solution based synthesis by thermolysing tin(II) chloride and thioacetamide in diethylene glycol at reaction temperatures of 180-220 °C. Triethanolamine was added to the diethylene glycol reaction medium to control the growth of the... 

LiB02 2H20 or Li20 20 4H2O, becomes the stable soHd phase. Dihydrate crystals are orthorhombic having a density of 1.825 g/mL and a stmctural formula Li[B(OH)4]. In solution above 150°C a hemihydrate, LiB02 1 /2H2O, forms and the anhydrous salt crystallizes above 225°C. 

The iron-carbon solid alloy which results from the solidification of non blastfurnace metal is saturated with carbon at the metal-slag temperature of about 2000 K, which is subsequendy refined by the oxidation of carbon to produce steel containing less than 1 wt% carbon, die level depending on the application. The first solid phases to separate from liquid steel at the eutectic temperature, 1408 K, are the (f.c.c) y-phase Austenite together with cementite, Fe3C, which has an orthorhombic sttiicture, and not die dieniiodynamically stable carbon phase which is to be expected from die equilibrium diagram. Cementite is thermodynamically unstable with respect to decomposition to h on and carbon from room temperature up to 1130 K... 

Figure 7.5 Phase diagram of elemental sulfur, showing the stable solid phases a-sulfur (orthorhombic red sulfur ) and /3-sulfur (monoclinic yellow sulfur ) and equilibrium phase boundaries (solid lines) as well as the metastable phase boundary (dashed line) that connects a-sulfur to liquid and vapor phases.

The half-width of the crystalline component line was estimated to be 18 Hz. This value reflects the very stable orthorhombic crystalline phase of this sample. The component line shape centered at 31.0 ppm represents the contribution from the amorphous phase in which the molecular conformations are changed rapidly over all permitted conformations. The relatively narrow line width estimated as 38 Hz is caused by the rapid molecular motion. The line centered at 31.3 ppm represents the noncrystalline phase in which the local molecular motion can occur in the same manner as in the amorphous phase (in Tic time frame), but a long-range molecular motion accompanying a conformational change related to a 10-20 methylene sequence is severely restricted. The wide line width as 85 Hz... 

Oxygen may be removed progressively by heating under controlled partial pressures of O2 between 400 and 950 °C. As oxygen is removed dismpting the CUO2 planes, Tc decreases. The orthorhombic phase is stable up to 5 = 0.5. Here a transformation to the tetragonal form takes place and is stable for 0.5 < 5 < 1.0, the end member of which is shown in... 

At higher temperatures the a-form transforms into the closely related tetragonal structure [26]. Very similar to NaBH4, KBH4 exhibits phase transformations from the cubic phase, stable at ambient conditions, to a tetragonal phase at about 4 GPa and an orthorhombic phase at 7 GPa [27]. 

The stable structures except for orthorhombic phase and surface electronic structure of LiBH/ ° were also investigated theoretically. 

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