51V MAS NMR spectroscopy: determination of quadrupole and anisotropic shielding tensors, including the relative orientation of their principal-axis systems

51V magic angle spinning NMR in VOPO4 phases

“…Recently, the electrochemical behavior of the different phases of VOPO 4 has been investigated. 4 -7 These studies confirmed that VOPO 4 is promising as a cathode material with an electrochemical potential close to 4 V and a theoretical specific capacity of 165 mA h g 1 . Note that these compounds are already used in the chemical industry as catalysts for the synthesis of maleic anhydride from n-butane or n-butene.…”

“…The MAS spectra are observed to break up into spinning sidebands (ssbs) and the absence of significant quadrupolar secondorder shifts indicates that the quadrupole coupling constant Q CC D e 2 qQ/h is moderate (jQ CC j < 3 MHz). 1,2,22,23 Indeed, the good agreement between the experimental and calculated data (Figs 1 and 2) demonstrates that the complete manifolds of ssbs from all seven 51 V transitions are detected. For simplicity, in Figs 1 and 2, the isotropic peak, determined from spectra employing different spinning speeds, was arbitrarily chosen as the chemical shift reference.…”

“…Since the isotropic shift and the line broadening need not be included in the optimization, the fit of the ssb intensities yields in principle the following seven parameters: the chemical shift (CS) anisotropy υ CS and its asymmetry parameter Á CS , the absolute value of the quadrupole (Q) coupling constant jQ CC j and corresponding asymmetry parameter Á Q , and the Euler angles , and , which transform the CS tensor from its principal axis system (PAS) into the PAS of the Q tensor. 1,3,19 In our case, it is nevertheless useful to consider the crystallographic symmetry. Indeed, the presence of a fourfold rotation symmetry at the vanadium site in˛I I -VOPO 4 Figure 1 shows that the 51 V MAS NMR results are in good agreement with these symmetry requirements, the corresponding two-parameter fit at the three available magnetic field strengths giving υ CS D 928 š 14 ppm and jQ CC j D 630 š 12 kHz (Table 1).…”

The Relationship Between 27Al Quadrupolar Parameters and AlF63– Octahedron Connectivity in Crystalline and Glassy Fluoroaluminates

“…The recycle delay was set at 1 s. Under these experimental conditions the relative peak intensities are quantitative. The reconstructions of these spectra were achieved using an in-house FOR-TRAN 95 code based on the theoretical treatment developed by Skibsted et al, [1,53] and including a correction for the second-order frequency shift, the formula for which is given in ref. [54,26] The adjustable parameters for the crystalline compounds are the quadrupolar frequency, ν Q , the asymmetry parameter, η Q , and the chemical shift tensor, δ.…”

Using hyperbolic secant pulses to assist characterization of chemical shift tensors for half‐integer spin quadrupolar nuclei in MAS powder samples

“…Hayashi and Hayamizu [28] have estimated the 51 V principal components of the CS tensors from NMR spectra obtained from stationary powder samples of some alkali metal and ammonium metavanadates and compared their results with those reported previously. Skibsted et al [29] have shown that by analysis using an iterative-fitting program of the entire ssb manifold obtained from the 51 V NMR spectrum of MAS powdered samples of NH 4 VO 3 and V 2 O 5 , it is possible to obtain all of the parameters describing the quadrupolar and CS interactions. Oldfield et al [32] have measured the 51 V NMR spectra of a powder sample of NaVO 3 both at the magic angle and slightly off the magic angle (by ∼1…”