Nuclear Quadrupole Relaxation in Silver and Sodium Halide Crystals

Anomalous Reconstructions of the (001) Surfaces of AgBr and NaCl

“…Since the HAS experiments are most sensitive to the topmost layer only its structural changes are observed. A possible explanation for the observed behavior is shown to be related to bulk studies on the creation and ordering of point defects inside AgBr by Nield et al [10], Goessens et al [11], and Voll et al [12] using neutron diffraction and transmission electron microscopy (TEM), respectively, as well as NMR measurements by Yamanishi et al [13,14] for both bulk AgBr and bulk NaCl.…”

“…A key indication as to the driving force for the reconstruction comes from measurements of the temperature dependence of the nuclear relaxation rate of 79 Br and 35 Cl in AgBr and NaCl by Yamanishi et al [13,14]. They observed that for AgBr and NaCl over a wide temperature range the relaxation rate can be fitted with a straight line.…”

“…This model also provides a plausible explanation for the initial extended annealing to temperatures well above T c required to activate the surface possibly by generating a large number of Ag 1 interstitials in the bulk, which segregate to the subsurface layer. The transition to the ͑1 3 1͒ structure is due to the increased mobility at temperatures above T c [13,14]. One possible mechanism involves the interstitial Ag 1 ions leaving the "͑2 3 2͒" lattice sites as a result of their hopping between all available tetrahedral interstitial sites, which have a ͑1 3 1͒ symmetry with respect to the (001) plane and, on average, a ͑1 3 1͒ diffraction pattern is observed.…”

Solid-state NMR of quadrupolar halogen nuclei

“…Examples include using the temperature dependence of T 1 in NaCl and AgCl to calculate defect migration, the pressure and temperature dependence of d iso ( 35 Cl) in RbCl, and the effect of elastic strain on the chlorine CT line shape in NaCl, amongst others [39,[77][78][79][80][81].…”

NMR Study on the Chemical Bonding and the Ionic Conductivity in Noble Metal Halides

“…From this point of view, we previously carried out the comparative NMR study on AgX, and NaX (X¼Cl, Br, I) crystals which have the rock-salt (RS) structure. 1,2) From the temperature dependence of the nuclear quadrupole relaxation rate 1=T 1 , we estimated the degree of covalency in these halides, which was 21{25% in silver halides and at most 2% in sodium halides; afterwards, the value of 0.3% was reported for NaI. 3) The covalency of silver halides has been found to be an order of magnitude larger than that of sodium halides.…”