Nickel interatomic distance

The radii in the lowest row of the table were obtained by a number of approximate considerations. For instance, if we assume the bismuth radius to bear the same ratio to the interatomic distance in elementary bismuth as in the case of arsenic and antimony, we obtain (Bi) = 1.16— 1.47 A. A similar conclusion is reached from a study of NiSb and NiBi (with the nickel arsenide structure). Although the structures of the aurous halides have not been determined, it may be pointed out that if they are assumed to be tetrahedral (B3 or Bi) the interatomic distances in the chloride, bromide, and iodide calculated from the observed densities1) are 2.52, 2.66, and 2.75 A, to be compared with 2.19, 2.66, and 2.78 A, respectively, from pur table. 

There are 2.56 d orbitals available for bond formation. To form 5.78 bonds these would hybridize with the s orbital and 2.22 of the less stable p orbitals. In copper, with one electron more than nickel, there is available an additional 0.39 electron after the hole in the atomic d orbitals is filled. This might take part in bond formation, with use of additional Ap orbital. However, the increase in interatomic distance from nickel to copper suggests that it forms part of an unshared pair with part of the bonding electrons, thus decreasing the effective number of bonds. 

Mean cobalt-cobalt and nickel-nickel distances observed in these complexes are very close to interatomic distances determined at ambient temperatures in cobalt and nickel metals (Co-Co 2.489(7) A vs. 2.507 A in a-cobalt (33) Ni-Ni 2.469(6) A vs. 2.492 A in the metal (39)). The mean M-H bond lengths, as well as hydride displacements from M3 faces, are less for nickel in H3Ni4(Cp)4 than for cobalt in HFeCo3(CO)9(P(OMe)3)3. Although the differences are marginally significant within error limits (Ni-H 1.691(8) A vs. Co-H 1.734(4) A displacements from plane Ni3 0.90(3) A vs. Co3 0.978(3) A), they are in the expected direction since the covalent radius should vary inversely with atomic number within a transition series. However, other effects such as the number of electrons in the cluster also can influence these dimensions. 

Other Covalent Radii.—Bipositive nickel, palladium, and platinum and tripositive gold form four coplanar dsp bonds, directed to the comers of a square, with attached atoms. Examination of the observed values of interatomic distances reveals that square dsp radii of atoms have the same values as the corresponding octahedral d sp radii, as given in Table 7-15. This is shown by the comparisons on the following page. 

Bipositive copper often forms four strong bonds directed toward the comers of a square. The observed interatomic distances correspond to the radius 1.28 A, about 0.08 A larger than for square-ligated nickel (II) the increase is to be attributed to the presence of the extra elec-... 

In the crystal structure of nickel asenide, NiAs, the As atoms are in hep with all octahedral interstices occupied by the Ni atoms, as shown in Fig. 10.2.3(a). An important feature of this structure is that the Ni and As atoms are in different coordination environments. Each As atom is surrounded by six equidistant Ni atoms situated at the corners of a regular trigonal prism. Each Ni atom, on the other hand, has eight close neighbors, six of which are As atoms arranged octahedrally about it, while the other two are Ni atoms immediately above and belowitatz = c/2. The Ni-Ni distance is c/2 = 503.4/2 = 251.7 pm, which corresponds to the interatomic distance in metallic nickel. Compound NiAs is semi-metallic, and its metallic property results from the bonding between Ni atoms. In the NiAs structure, the axial ratio da = 503.4/361.9 = 1.39 is much... 

Figure 31 describes the structure of the [Ni Me2Ga(N2C3H3)2 2] island of the bis-[dimethyl bis(pyrazol-l-yl)gaUato]nickel(II) complex ) in which the islands are only mutually held together by means of van der Waals forces. The interatomic distance of... 

Although the dithiocyanate (XXVI) is ionic in aqueous ethenolic solution, a later x-ray analysis (1959) showed that in the crystalline state the nickel atom is at the center of an octahedron, being coordinated to the four amino groups of the tetramine and to the nitrogen atoms of the two thiocyanate groups, the interatomic distances being Ni-N(primary) 2.20, Ni-N(tertiary) 2.13, and Ni-N(NCS) 2.06 A. (4 ). 

Third, the doublet and, especially, sextet models require very precise superimposing of the molecule on the catalyst lattice. We have found that the cyclohexane derivatives, in accordance with the sextet model, smoothly dehydrogenate only on the following metals nickel, cobalt, iridium, palladium, platinum, ruthenium, osmium, and rhenium, all of which crystallize in Al, A3 lattices with certain interatomic distances. These results extend to the alloys of these metals. The catalytic activity of rhenium for this reaction was predicted by the multiplet theory as this metal maintains the square of activity this prediction was realized experimentally in the laboratory of the author. Similar correlations take place in the exchange of cyclanes with deuterium. 

The constitution of the platinum complex has been elucidated by crystal structure investigation 82), and the molecule (XXXVa-e) has been found to be completely planar. The interatomic distances and bond angles are given in Fig. 2. As would be expected, the nickel compound is diamagnetic, and the cobalt and iron compounds show paramagnetism, corresponding with one and two unpaired d-electrons, respectively 41). These... 

Using the Debye model, compute the root-mean-square displacement of nickel at 300 K and at its melting point. What is the fractional displacement of the metal atoms relative to the interatomic distance at the melting temperature ... 

Reference to the bond angles and interatomic distances for these molecules shows that as far as the carbon atoms are concerned their values are little different from those of the olefin molecule. It would be expected, therefore, that catalysts which were effective for hydrogenation of the latter would also function with the heterocyclic molecules. This is found to be so, in that nickel catalysts are known to give tetrahydrofuran and pyrrolidine by the hydrogenation of furan and pyrrole at 180° (Padoa, 25). Tetrahydrofuran is also formed by the use of platinum (Starr and Hixon, 26), osmium, or palladium (Shuikin, Nikiforov, and Stolyarova, 27) as the catalyst, and pyrrolidine is similarly produced by palladium or rhodium catalysts (Zelinskii and Yurev, 28). In all these metals there are spacings of the atoms very similar to those in metallic nickel, the hexagonal osmium lattice having a equal to 2.71 A. 

These considerations can also be applied to other metals. Thus die (100) planes of metals with larger atomic spacings than nickel (e.g., Pd, Pt, and Fe) should exhibit weaker chemisorption, and the same should also be true of metals with shorter interatomic distances such as tantalmn. Figure 5-19 shows the rate of ethylene hydrogenation as function of metal-metal distance (volcano plot). 

Inspection of the details of the calculation shows that the positive contributions to I arise from electron-electron or nucleus-nucleus interactions in the energy term of the operator H. Thus they will be most evident when there is a considerable overlap of electron clouds, which occurs most markedly in atoms possessing d and / electrons (quantum number 1 = 2 and 3). This factor tends to locate ferromagnetism in transition elements. For electron overlap to outweigh electron-nucleus interaction, the nuclei should not be too close. Nor, on the other hand, should they be too far apart, or aU interaction of any kind becomes feeble. This factor makes for further specificity, and in fact for the elements iron, cobalt, and nickel the ratio (interatomic distance/radius of d electron shell) does lie within a special rather narrow range. 

We may well expect that the strongest bonds would have the shortest interatomic distances, and it is accordingly not surprising that the large interatomic distances shown in Figure 17-2 are those for soft metals, such as potassium the smallest ones, for chromium, iron, nickel, and others, refer to the strong, hard metals. 

The radial distribution function, g(r), is proportional to the density of atoms at the distance R from a certain atom taken for the central atom. The pair correlator is directly comparable to the structural factor obtained from the experiments on the X-ray scattering and it provides only the information on interatomic distances. Figure 6.1 shows the calculated Cu, Ni and Au RDFs in supercooled state in comparison with the experimental data by Waseda [ 14]. It should be noted that there is good correspondence for gold. For copper and nickel the correspondence of the calculated and experimental RDFs is satisfactory. The discrepancy can be explained by the inaccuracy of the used interatomic interaction potentials. Nevertheless, the first RDF peak for all metals under study is very well reproduced, which allows to speak about the adequacy of further analysis of the cluster structure of the melts. Moreover, the discrepancy of the calculated and experimental RDFs allows to clarify the degree of the influence of the accuracy of the interatomic interaction description on the cluster structure by the comparison of the results with those in Refs. [7-9], where the exacter ab-initio methods of simulation were used. 

The structure was determined by a single-crystal method, R = 0.040 (Babizhets ky et al. 1992b). Lai and La3 atoms have CNs of 20 and for La2 CN is 23. Nickel atoms (except Nil) are situated in orthorhombic prisms with additional atoms outside the rectan ar faces of the prisms (fig. 41). The atomic arrangement of Ni7 is a 13-vertices polyhedron. The phosphorus atoms have trigonal-prismatic coordination with 3 or 4 (P4) ad(htional atoms. Interatomic distances are close to the sum of the respective atomic... 

The structure was determined by a single-crystal method, 7i = 0.0545 (Chykhrij et al. 1990). All nickel atoms have CPs in the form of orthorhombic prisms with centered square faces, the phosphorus atoms are in trigonal prisms (fig. 42). The shortest interatomic distances are Ndi N(ii= 5Nd2-Nd2 = 0.3759 5Nai Ni6 = 0.2996 <5Nd2-P3 = 0.287 Ni3-Ni6 = 0.243 6Ni3-P3 = 0.216. 

The structure of CegNiisPio was determined by a single-crystal method, 7 = 0.042 (Babizhets ky et al. 1993a). It is also closely related to NdsNiyPs. In Nd3Ni7Ps the columns of octahedra [DNig] are filled with Ni6 atoms which occupy 22% of the positions 6(/i) Ay 1/4 (x = 0.0412, y = 0.0684), while in CegNijsPio these positions with close coordinates are fully occupied by nickel atoms. The atomic coordinates of all other atoms do not differ essentially from those in NdsNiyPg. The shortest interatomic distances are 6ce-Ni = 0.3009 6ce-p = 0.3020 Ni-Ni=0.2765 6Ni-P=0.2310. 

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