Calcium interatomic distance

The closest M-M approach in these compounds is often less than for the metal itself this should occasion no surprise since this is a common feature of many compounds in which there is substantial separation of charge. For example, the shortest Ca-Ca interatomic distance is 393 pm in calcium metal, 360 pm in CaH2, 380 pm in CaF2, and only 340 pm in CaO (why ). 

Tabie 14 Interatomic distances (A) in Sr8Rli5D23 and calcium analog... 

The first three lanthanides, La, Ce and Pr, are dimorphous metals, with h.c.p. and Lc.c. structures differing little in density. The others are h.c.p. except Eu (b.c.c.) and Yb (f.c.c.) in which two the interatomic distances are greater and the densities lower (Table 95). The physical constants of the lanthanides are known only approximately the first ionisation potentials are about 6 cV and the second about 12 eV, comparable with those of calcium. The standard electrode potentials, Ln +/Ln, are all about —2.1 V. 

As mentioned previously in Section 13.1, shorter Ca-Ca interatomic distance results in higher hydraulic activity of calcium silicates. The computed distances within 4 A between the neighboring calcium atoms in the doped supercell are shown in Table 13.4. Ca-Ca bond lengths are 3.5585 A and... 

These are not very oommon minerals, and the only example included here is vesuvianite. This is a complex structure with both isolated silica tetrahedra and sorosilicate groups. The ideal formula is Cai9AltFe(Al,Mg,Fe)8Sii807o (0H)8- The calcium is eight coordinated, aluminum is six coordinated, the disordered site is six coordinated and iron is both six and five coordinated. There are disordered sites in the structure which complicates the minerals. The interatomic distances are shown in Table 4.10 and the structure is shown in Figure 4.15. 

A calculation based on the decrease of the electron density at the surface and on the relaxation of the top lattice plane resulted22 in values such as 190 and 1234 erg/cm2 for the 100 faces of sodium and aluminum, respectively. The above relaxation, that is, the ratio of the interplanar distance in bulk to that in the external region was calculated23, assuming a Morse type interatomic potential. The above ratio appeared to be, e.g., 1.13 for the 100 face of calcium, and 1.016 for the 111 face of lead. The relaxation lowered the energy 7 by 0.5 to 7% for different metals and crystal faces. 

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