Probing the YD3 structure by H-2 NMR electric-field gradients: A comparison with first-principles calculations - art. no. 214110

Electric-field gradients (EFG's) in yttrium trideuteride (YD2.98) have been determined using deuteron magnetic resonance (DMR) and compared with value s for the P (3) over barc 1 and P6(3)cm structures calculated from first pr inciples. The experimental DMR spectra at low temperatures (180-290 K) coul d be decomposed into two components with intensity ratio 2:1 in accordance with the expected two groups of deuterium sites, i.e., tetrahedral and octa hedral sites in the crystal lattice. Their characteristic quadrupole freque ncies, nu (q), and asymmetry parameters, eta, have been compared with the t heoretical values obtained for the structures with space groups P (3) over bar c1 (no. 165) and P6(3)cm (no. 185). The agreement between the experimen tal and calculated results is such better for the latter structure. The spe ctra at higher temperatures (300-370 K) transform from a two-component conf iguration into three quadrupolar doublets plus a low-intensity narrow centr al component. One of the doublets keeps the same parameters as those observ ed at low temperatures. The two others indicate changes in the tetrahedral site environments. One possible explanation could be a thermally activated quasi-two-dimensional hopping of the D atoms to nearby sites within the ab plane.