Crystal structure 2232, Tables

It should be emphasised that it is the rule rather than the exception for p to change markedly with crystal structure (Table 8.2). It is therefore unwise to assume that various metastable allotropes can be given the same value of P for the stable structure. In some cases values of p can be extrapolated from stable or metastable alloys with the requisite crystal structure, but in others this is not possible. A significant development is that it is now possible to include spin polarisation in electron energy calculations (Moruzzi and Marcus 1988, 1990a,b, Asada and Terakura 1995). This allows a calculation of the equilibrium value of to be made in any desired crystal structure. More importantly, such values are in good accord with known values for equilibrium phases (Table 8.2). It has also been shown that magnetic orbital contributions play a relatively minor role (Eriksson et al. 1990), so calculated values of P for metastable phases should be reasonably reliable. 

An extensive series of i/2-hydrazido(l —) complexes of titanium have recently been reported467 together with X-ray crystal structures (Table 17). The bonding of the >/2-hydrazido fragment is perceptibly less symmetrical than for the Mo and W complexes due to increased multiple bonding between Ti and the monosubstituted nitrogen. 

These form the largest single group of hetero-Pt clusters, with more than 40 crystal structures (Table V) reported. Their chemistry, particularly with regard to triosmium-platinum species, is the most developed of any hetero-Pt clusters. 

Tabushi et al. (1981) suggested that the 15-hedron (51263) is absent from Figure 2.5 and in all clathrates except bromine due to an unfavorable strain relative to the other cavities in si and sll. In their review of simple and combined cavities, Dyadin et al. (1991) suggested that in addition to the cavities found in si, sll, and sH, there are 4258 and 51263 cavities. In Jeffrey s (1984) list of a series of seven hydrate crystal structures (Table 2.3), additional cavities to those found in si, sll, and sH are 51263, 4454,43596273, 4668. 

Green (crystal structure Table 40) Orange-red, tram (P,P) and trans (P,N) isomers, enantiomers resolved 13C NMR, visible-UV Yellow optical isomers separated... 

K,-A,A-[Co(L)3]-3H20 c2or Resolveid using (—)5g -[Ni(phen3)]2+ Racemizes in soln. 24 h some oxalate exchange (crystal structure, Table 61) 2,3... 

The continually increasing importance of iron oxide pigments is based on their nontoxicity, chemical stability, wide variety of colors ranging from yellow, orange, red, brown, to black, and good performance/price ratio. Natural and synthetic iron oxide pigments consist of well-defined compounds with known crystal structures (Table 3.1) [3.1, 3.2]. 

Our simulations shows that both CTWAT and CTMONO have lower RMS deviations compared to the CT system, indicating that they have a closer resemblance to the starting crystal structure (Table l).If we assume that CTMONO represents an aqueous simulation, this is in contrast to our earlier work on BPTI where we found that the RMS deviation was on average higher for the BPTI in water system. This difference is more obvious in the RMS deviation of the backbone atoms only. We further found the change in the placement of the 50 "essential" water molecules from CT to CTWAT have resulted in significant difference in RMS deviations. It has been reported that the correct placement of buried water molecules is necessary to obtain locally correct structure. ... 

These phase changes are accompanied by changes In the crystal structure (Table 2). The changes are quite slgnificantp and It Is not surprising that phase transformation leads to loss of surface area. 

The Rietveld plots of both powder diffraction data sets are shown in Figure 7.10 and Figure 7.11. Visual analysis of both figures indicates a good fit, which was expected from the low residuals Table 7.7). The model of the crystal structure Table 7.8) appears to be complete and makes both physical (reasonable atomic displacement parameters) and chemical sense [no overlapping atoms, the 3(g) sites are occupied simultaneously by atoms that have close atomic volumes (Ni and Sn), the chemical composition of the major phase established from x-ray data is nearly identical to the known composition of the alloy]. Therefore, the outcome of this crystal structure determination may be accepted as satisfactory. 

Bonding within the silicate layers is predominantly ionic. As a result, forces are undirected and ion size plays an important role in determining crystal structure. Table 5.1 shows the crystal radii of common ions in silicates. The distance between two adjacent ions in a crystal can be measured accurately by x-ray methods. From a series of such measurements between different ions, the effective contributing radius of each ion can be determined. An ion has no rigid boundary an ion s radius depends on the number of its orbital electrons and on their relative attraction to the ion s nucleus. The radius of Fe ions, for example, decreases from 0.074 to 0.064 ran... 

H2P30, can act as a monodcntate (terminal O"), bidentate (P,y, six membered a.,y, eight membered) and tridentate (a,P,y, six membered) ligand system (crystal structures Table 46). The p,y six-membered chelate is particularly interesting since it is the only structure to have an asymmetric P centre. Although prepared from [Co(NHj)4(0112)2] HjPsO] as a racemic mixture, the crystal... 

McGovern and Shoichet performed a detailed comparative study using both apo and holo crystal structures and homology models of nine enzymes [48]. In general, they found that best results were obtained with the holo crystal structure (Table 14.2). 

---