Oxygen coordination number

Concomitant with the change in the oxygen coordination number is a shift of the first minimum of the O-H RDF from 1.30 A at 34 GPa to 1.70 A at 115 GPa. We observe a similar structural change in the H-H RDF in which the first peak lengthens from 1.63 A (close to the result for ambient conditions) to 1.85 A. These observations bear a strong resemblance to the ice VII to ice X transition in which the covalent O-H bond distance of ice becomes equivalent to the hydrogen bond distance as pressure is increased.82 However, the superionic phase differs from ice X, in that the position of the first peak in g(RoH) is not half the distance of the first 0-0 peak.82 We analyze the effect... 

The reaction of platinum dioxide with other metal dioxides can be separated into three groups—i.e., compounds with metal-oxygen coordination numbers of 4 2, 6 3, and 8 4. We have investigated only a single... 

Si-0 bond distance is determined largely by the oxygen coordination number and the number and type of polyhedral contacts. 

Polarizing power of network modifier (z/r ) Concentration of nonbridging oxygens Coordination number of certain cations Type of structural groupings in glass Melting conditions Photochemical reactions Multivalent additives Impurities... 

Compounds of the first group, complex oxides, maybe regarded as assemblies of ions of two (or more) metals and 0 ions. The numbers of oxygen ions surrounding the cations (their oxygen coordination numbers) are related to the sizes of the ions (Chapter 7). These coordination numbers are high (up to 12) for the largest ions, for example, Cs and Ba , and usually vary, within certain limits, in different structures. The crystal structures of complex oxides are described in Chapter 13. 

Regarding the A Os-ZrOa mixed oxides, the cationic radius of Zr (0.079 nm) is larger than those corresponding to Ti and in octahedral coordination (0.060 and 0.053 nm, respectively) [15]. Moreover, its oxygen coordination number (seven or eight) is very different to that of the cationic positions in a pseudospinel structure (four- or sbc-coordinated). Owing to that, it is not probable that Zr" cations could enter the AI2O3 matrix. 

Oxygen coordination number Oxide Type I Frequency (cm Type 11 Type 111 Type IV... 

The Roman numbers at the upper left of RE are the oxygen coordination numbers. 

Up to — 1 types of hydroxyls can be detected on the surface of a given oxide (where n is the oxygen coordination number in the bulk). Thus, only type I hydroxyls can be formed on silica, because the oxygen coordination number is 2 (see Table 2.2). 

The oxygen coordination number of the network cation is small. 

Handke et al. [101] on the basis of inlia-ied and Raman spectroscopic studies advanced the hypothesis that the stractuie of triclinic C3S seems to be laminar and is composed of the layers of Cla2[SiOJ and CaO. The symmetiy of single layer being close to the R3m symmetiy, proposed by Jeffeiy. This laminar C3S stmcture could explain its non-Hstoichiometiy and easy decomposition into C2S and CaO. In C3S stmcture proposed by Belov et al. [102] the oxygen coordination number (CN=6) non belonging to SiO tetrahedra is also close to octahedral coordination, existing in CaO crystals. 

The structure of (CH )jNCl(SeOClj) illusuates that even larger neutral molecules than water and ammonia can be incorporated into an ionic crystal structure. Furthermore the arrangement around the anion (Cl") can be compared with that of cations in those hydrates for which the oxygen coordination number of the cations is greater than the available number of water molecules. 

In this chapter, we present some latest analysis results of lanthanides (Lns Eu and Gd)-M6ssbauer structure and powder X-ray diffraction (XRD) lattice parameter (oq) data of defect-fluorite (DF) oxides with the new defect crystal chemistry (DCC) Oq model [ 1,2] as an upgrade of the former random oxygen coordination number (CN) Oq model [3,4]. This is, thus, the first report of our ongoing efforts to further elaborate the model and extend its applicability to more various systems, especially to pyrochlore (P)-type stabilized zirconias (SZs) and stabilized hafnias (SHs). 

In the series of compounds of the type MP04 (0-0.5) H2O, there are four monodentate and two bidentate tetrahedra linked to the metal, forming a hexagonal network with open, oxygen-lined channels that hold zeolitic water. When this water is driven out by high temperature, a different, more dense, structure is obtained which is isomorphous with the mineral monazite. The metal atom retains its same oxygen coordination number. 

Here, Z is the oxygen coordination number and Rqu and Rum are the proton-oxygen and proton-cation inter-atomic distances. By neglecting the proton radius, Rhm is approximated by the anion-cation inter-atomic distance in the oxide. The main difference between this expression and Parks formula (6.4.1) lies in the value of the positive charge. Each of the... 

Z cations in the neighbourhood of the oxygen atom contributes as q. The pK associated with acidic or basic reactions thus depends in a linear way upon the oxygen coordination number Z ... 

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