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Defect structures and nuclear electric hyperfine interactions have been investigated in a series of binary Ni–Al, Ni–Ga, Ni–In intermetallic compounds, and the shape memory compound NiTi using 27Al, 47,49Ti, 61Ni, 71Ga and 115In nuclear resonance. Components of the 61Ni NMR spectrum for a series of cubic Ni1−xAlx and Ni1−xGax specimens on either side of x = 0.5 have been identified as due to Ni substitutions and Al (or Ga) vacancies. For stoichiometric NiAl, Ni2Al3 and NiAl3 the 61Ni lines are narrow and distinguished by well-separated Knight shifts, although the 61Ni lineshape for the ordered vacancy compound Ni3Al4 indicates a substantial nuclear quadrupole interaction at the Ni site. The substitution for Al of the group III elements Ga and In, which have isoelectronic outer shells, acts to increase the 61Ni Knight shift such that 61K(Al)<61K(Ga)<61K(In). This trend is observed not only for cubic NiAl and NiGa, but also for trigonal Ni2Al3, Ni2Ga3 and Ni2In3. In NiTi the sharp first-order transition between the (high-temperature) cubic phase and the (low-temperature) monoclinic phase has been observed while monitoring the 61Ni and 49,47Ti NMR lineshapes as a function of temperature. In the non-cubic phases of these materials (including hexagonal ε-NiIn) the electric field gradient tensor components Vzz and η at the atomic sites have been determined from the nuclear quadrupole perturbed 27Al, 47Ti, 61Ni, 71Ga NMR lineshapes together with 69Ga and 115In NQR transition frequencies, and compared with values derived from ab initio calculation.

The alloy system has been investigated by means of NMR around the equiatomic region where x = 0.5, and at x = 0.6, which gives the trigonal ordered compound . For , two Al sites were clearly resolved at room temperature by means of their characteristic second-order quadrupolar structure. NMR spectra for cubic taken at temperatures up to show rapid line narrowing above for x = 0.54 (indicative of diffusion processes), but no such line narrowing was observed up to for x = 0.50 or x = 0.48. NMR results are also reported for the equiatomic alloy. For , the NMR powder pattern evolved smoothly into that characteristic of one well defined site as the temperature was raised to , although no phase transition was detected by means of powder x-ray diffraction or thermal analysis. These observations are discussed qualitatively in terms of defect-assisted diffusion processes.

Both direct absorption curves and derivative curves due to proton magnetic resonance absorption in wool have been obtained. Peak heights and widths of the absorption lines were measured for wool samples equilibrated at a number of relative humidities in the range 0 to 90%. All water protons in wool appear to be less firmly bound than the keratin protons, but less mobile than liquid water. It seems clear that an increment of absorbed water changes the binding energies of previously absorbed water. No evidence was obtained of a subdivision of water in wool into two or three fractions with different binding energies which are successively bound as the equilibrium regain is increased.--------

Studies at other temperatures might be helpful in interpreting the results. With this in mind we have also calculated the widths of HCI+DCI and DCI+HCI which are expected at dry-ice temperature. The relatively small changes predicted suggests that this would not be a particularly definitive experiment, but it is probably worth checking.While the conclusions to be drawn are somewhat less definite than was originally hoped, some general remarks may be made. The determination of a quadrupole moment from these two experiments is not feasible. Nevertheless, the general validity of Anderson's theo-THE JOURNAL OF CHEMICAL PHYSICS retical work is certainly clearly established in that calculations appear to yield results of the correct order of magnitude. That one must include nonresonant collisions in this work seems to be certain, since calculations which consider only very nearly resonant collisions would predict much reduced values of the linewidths. ACKNOWLEDGMENT We are indebted to Dr. W. S. Benedict for extremely helpful comments and criticisms and for providing us with the results of his linewidth calculations prior to publication.Resonance data have been obtained for the intracrystalline water in homo-ionic vermiculite, montmorillonite, and hectorite in both the crystalline and osmotic swelling regions, but interpretation is complicated by the anisotropic susceptibility of the crystals and the effects of particle size, discussed briefly in an appendix. Because of this, only a minimum value can be obtained for the proton mobility, and it is shown that in the osmotic swelling region molecular motion may not be very different from that in free water. The proton mobility in the crystalline swelling region varies with the water content. A single-crystal study of vermiculite containing two sheets of water between silicate layers shows that the water molecules are in hindered rotational movement. A transition to a freely reorienting phase is dependent on particle size. The results are applied to some aspects of the theory of gels and of interparticle forces.