First-principles calculations of 17O nuclear magnetic resonance chemical shielding in Pb(Zr_(1/2)Ti_(1/2))O_3 and Pb(Mg_(1/3)Nb_(2/3))O_3: Linear dependence on transition-metal/oxygen bond lengths

摘要

First-principles density functional theory oxygen chemical shift tensors were calculated for A(B,B′)O_3 perovskite alloys Pb(Zr _(12)Ti_(12))O_3 (PZT) and Pb(Mg_(13)Nb _(23))O_3 (PMN). Quantum chemistry methods for embedded clusters and the gauge including projector augmented waves (GIPAW) method [C. J. Pickard and F. Mauri, Phys. Rev. B 63, 245101 (2001)]10.1103/PhysRevB.63.245101 for periodic boundary conditions were used. Results from both methods are in good agreement for PZT and prototypical perovskites. PMN results were obtained using only GIPAW. Both isotropic _(iso) and axial _(ax) chemical shifts were found to vary approximately linearly as a function of the nearest-distance transition-metal/oxygen bond length, r_s. Using these results, we argue against Ti clustering in PZT, as conjectured from recent ~(17)O NMR magic-angle-spinning measurements. Our findings indicate that ~(17)O NMR measurements, coupled with first-principles calculations, can be an important probe of local structure in complex perovskite solid solutions.