Determination of the ³¹P and ²⁰⁷Pb Chemical Shift Tensors in Pyromorphite, Pb₅(PO₄)₃Cl, by Single‐Crystal NMR Measurements and DFT Calculations

Abstract

Abstract. The chemical shift (CS) tensors for 31 P and 207 Pb in the natural mineral pyromorphite, Pb 5 (PO 4 ) 3 Cl, were determined from orientation-dependent NMR spectra of a single crystal, and MAS-NMR spectroscopic experiments. For the two crystallographically independent lead atoms in the hexagonal crystal lattice with space group P6 3 /m, the NMR parameters derived from the tensor eigenvalues are δ iso = -2172 ppm, η cs = 0.08 for the 207 Pb at Wyckoff position 6h, and δ iso = -2810 ppm, η cs = 0.49 for position 4f. For the 31 P, which are also located at positions 6h, δ iso = -1.74 ppm and η cs = 0.21 was found. A multi-parameter fit was utilized to extract the tensors from spectra

How does the NMR thermometer work? Application of combined quantum molecular dynamics and GIPAW calculations into the study of lead nitrate

“…It is also worth to notice that the obtained σ iso depends significantly on the chosen functional, even in the most homogenous group of results received after “full” optimization, the range of the calculated σ iso exceeded 150 ppm <8997 ppm; 9156 ppm>. This may be the reason for the previously reported inconsistencies between the experimentally obtained and calculated using GIPAW NMR parameters for Pb atoms in various compounds, as in those cited works the calculations were performed using the PBE functional solely.…”

“…Firstly, as the geometry optimization at 0 K was only an introduction to the main part which was the dynamics at chosen temperatures, any saving of computational time resulting from not overestimating the calculations quality criteria would be especially beneficial. Secondly, as the previously published GIPAW calculations for Pb atoms have been found to be very inaccurate, it was important to ensure that the possible inconsistencies between the experimentally obtained and calculated values would not result from the calculations quality reasons.…”

“…It was demonstrated that lead nitrate can be used in MAS probes to measure sample temperature changes, temperature gradients, MAS heating effects, and the dynamics of temperature jumps . Besides, as the resonance frequency of the 207 Pb nucleus is very sensitive to changes in its local environment, the 207 Pb ssNMR analysis is often performed in the structural studies …”

“…Recently, in the series of publications, Zeman et al presented the results of the static (at 0 K) GIPAW calculations for lead compounds in which the large differences, exceeding thousands of ppm, between the calculated and experimental data for 207 Pb in the pyromorphite—Pb 5 (PO 4 ) 3 Cl and vanadinite—Pb 5 (VO 4 ) 3 Cl were reported. Surprisingly, the calculated NMR properties for the other elements (P, V, Cl) using the same method and parameters proved very accurate.…”

Single-Crystal 31P and 7Li NMR of the Ionic Conductor LiH2PO4

“…33), depicted in Figure 1b Berlin), with the crystallographic c axis and ab plane indicated by arrows. [10] (b) Wurtzite structure of AlN, according to Reference [9], viewed down the crystallographic (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) direction. The aluminum atoms (grey) and the nitrogen atoms (yellow), both located at Wyckoff position 2b, are tetrahedrally coordinated by each other with one Al-N bond directed parallel to the crystallographic c axis.…”